Haruki has 24 centimeters of wire. He cuts the wire and bends it into the following shapes, one at a time:
- A regular hexagon with side length 5 cm
- A square of area 36 cm²
- A right triangle whose legs are 6 and 8 cm long
Which of the shapes can Haruki make?
Haruki 有 24 厘米长的铁丝。他剪断铁丝并把它弯成以下形状,一次做一个:
- 边长为 5 cm 的正六边形 - 面积为 36 cm² 的正方形 - 两条直角边分别为 6 cm 和 8 cm 的直角三角形
Casey went on a road trip that covered 100 miles, stopping only for a lunch break along the way. The trip took 3 hours in total and her average speed while driving was 40 miles per hour. In minutes, how long was the lunch break?
Peter lives near a rectangular field that is filled with blackberry bushes. The field is 10 meters long and 8 meters wide, and Peter can reach any blackberries that are within 1 meter of an edge of the field. The portion of the field he can reach is shaded in the figure below. What fraction of the area of the field can Peter reach?
Peter 住在一块长方形黑莓地附近。这块地长 10 米,宽 8 米。他能够采摘到距离地块边缘 1 米范围内的所有黑莓。下图中阴影部分表示他能到达的区域。他能到达的区域占整块地面积的几分之几?
Mika would like to estimate how far she can ride a new model of electric bike on a fully charged battery. She completed two trips totaling 40 miles. The first trip used 1/2 of the total battery power, while the second trip used 3/10 of the total battery power. How many miles can this electric bike go on a fully charged battery?
Mika 想估算她新买的电动自行车充满电后最多能骑行多远。她完成了两次行程,总共骑行了 40 英里。第一次行程消耗了总电量的 1/2,第二次行程消耗了总电量的 3/10。这辆电动自行车充满电后最多能骑行多少英里?
A poll asked a number of people if they liked solving mathematics problems. Exactly 74% answered "yes." What is the fewest possible number of people who could have been asked the question?
Squares of side length 1, 1, 2, 3, and 5 are arranged to form the rectangle shown below. A curve is drawn by inscribing a quarter circle in each square and joining the quarter circles in order, from shortest to longest. What is the length of the curve?
In the figure below, each circle will be filled with a digit from 1 to 6. Each digit must appear exactly once. The sum of the digits in neighboring circles is shown in the box between them. What digit must be placed in the top circle?
The figure below shows a tiling of 1×1 unit squares. Each row of unit squares is shifted horizontally by half a unit relative to the row above it. A shaded square is drawn on top of the tiling. Each vertex of the shaded square is a vertex of one of the unit squares. In square units, what is the area of the shaded square?
Jami picked three equally spaced integer numbers on the number line. The sum of the first and the second numbers is 40, while the sum of the second and third numbers is 60. What is the sum of all three numbers?
Jami 在数轴上选取了三个等间距的整数。第一个数与第二个数之和为 40,第二个数与第三个数之和为 60。这三个数的总和是多少?
Elijah has a large collection of identical wooden cubes which are white on 4 faces and gray on 2 faces that share an edge. He glues some cubes together face-to-face. The figure below shows 2 cubes being glued together, leaving 3 gray faces visible. What is the fewest number of cubes that he could glue together to ensure that no gray faces are visible, no matter how he rotates the figure?
2026 AMC8 #17 · Counting, Probability & Statistics · ★★★
Four students are seated in a row. They chat with the people sitting next to them, then rearrange themselves so that they are no longer seated next to any of the same people. How many rearrangements are possible?
Miguel is walking with his dog, Luna. When they reach the entrance to a park, Miguel throws a ball straight ahead and continues to walk at a steady pace. Luna sprints toward the ball, which stops by a tree. As soon as the dog reaches the ball, she brings it back to Miguel. Luna runs 5 times faster than Miguel walks. What fraction of the distance from the entrance to the tree will Miguel have walked when Luna returns the ball to him?
Miguel 带着他的狗 Luna 散步。当他们走到公园入口时,Miguel 向前扔出一个球并继续匀速行走。Luna 冲向球,球停在一棵树旁。Luna 一拿到球就立刻跑回 Miguel 身边。Luna 的奔跑速度是 Miguel 步行速度的 5 倍。当 Luna 把球送回给 Miguel 时,Miguel 已经走了从入口到树这段距离的几分之几?
2026 AMC8 #20 · Counting, Probability & Statistics · ★★★
The land of Catania uses gold coins and silver coins. Gold coins are 1 mm thick and silver coins are 3 mm thick. In how many ways can Taylor make a stack of coins that is 8 mm tall using any arrangement of gold and silver coins, assuming order matters?
Catania 国使用金币和银币。金币厚 1 毫米,银币厚 3 毫米。Taylor 想用任意数量和顺序的金币与银币堆叠出一个总高为 8 毫米的硬币堆(顺序不同视为不同方式)。共有多少种堆法?
2026 AMC8 #21 · Counting, Probability & Statistics · ★★★
Charlotte the spider is walking along a web shaped like a 5-pointed star, shown in the figure below. The web has 5 outer points and 5 inner points. Each time Charlotte reaches a point, she randomly chooses a neighboring point and moves to that point. Charlotte starts at one of the outer points and makes 3 moves (re-visiting points is allowed). What is the probability she is now at one of the outer points of the star?
Charlotte 是一只蜘蛛,她在一张形如五角星的网上爬行(如下图所示)。这张网有 5 个外顶点和 5 个内顶点。每次 Charlotte 到达一个顶点时,会随机选择一个相邻顶点并移动过去(允许重复访问)。她从一个外顶点出发,共移动 3 次。此时她位于外顶点的概率是多少?
2026 AMC8 #22 · Counting, Probability & Statistics · ★★★★★
The integers from 1 to 25 are arbitrarily separated into five groups of 5 numbers each. The median of each group is identified. Let M equal the median of the five medians. What is the least possible value of M?
Lakshmi has 5 round coins of diameter 4 centimeters. She arranges the coins in 2 rows on a table top, as shown below, and wraps an elastic band tightly around them. In centimeters, what will be the length of the band?
The notation n! (read "n factorial") is defined as the product of the first n positive integers. (For example, 3!=1⋅2⋅3=6.) Define the superfactorial of a positive number, denoted by n!, to be the product of the first n factorials. (For example, 3!=1!⋅2!⋅3!=12.) How many factors of 7 appear in the prime factorization of 51!, the superfactorial of 51?
记号 n!(读作"n 阶乘")定义为前 n 个正整数的乘积(例如 3!=1⋅2⋅3=6)。定义超阶乘 n! 为前 n 个阶乘的乘积(例如 3!=1!⋅2!⋅3!=12)。在 51! 的质因数分解中,因子 7 出现了多少次?
In an equiangular hexagon, all interior angles measure 120°. An example of such a hexagon with side lengths 2, 3, 1, 3, 2, and 2 is shown below, inscribed in equilateral triangle ABC. Consider all equiangular hexagons with positive integer side lengths that can be inscribed in △ABC, with all six vertices on the sides of the triangle. What is the total number of such hexagons? Hexagons that differ only by a rotation or a reflection are considered the same.
Buffalo Shuffle-o is a card game in which all the cards are distributed evenly among all players at the start of the game. When Annika and 3 of her friends play Buffalo Shuffle-o, each player is dealt 15 cards. Suppose 2 more friends join the next game. How many cards will be dealt to each player?
Betty drives a truck to deliver packages in a neighborhood whose street map is shown below. Betty starts at the factory (labled F ) and drives to location A , then B , then C , before returning to F . What is the shortest distance, in blocks, she can drive to complete the route?
Sekou writes the numbers 15, 16, 17, 18, 19. After he erases one of his numbers, the sum of the remaining four numbers is a multiple of 4. Which number did he erase?
2025 AMC8 #7 · Counting, Probability & Statistics · ★★
On the most recent exam on Prof. Xochi's class,
5 students earned a score of at least 95% ,
13 students earned a score of at least 90% ,
27 students earned a score of at least 85% ,
50 students earned a score of at least 80% ,
How many students earned a score of at least 80% and less than 90% ?
Isaiah cuts open a cardboard cube along some of its edges to form the flat shape shown on the right, which has an area of 18 square centimeters. What is the volume of the cube in cubic centimeters?
2025 AMC8 #9 · Counting, Probability & Statistics · ★★
Ningli looks at the 6 pairs of numbers directly across from each other on a clock. She takes the average of each pair of numbers. What is the average of the resulting 6 numbers?
In the figure below, ABCD is a rectangle with sides of length AB = 5 inches and AD = 3 inches. Rectangle ABCD is rotated 90∘ clockwise around the midpoint of side DC to give a second rectangle. What is the total area, in square inches, covered by the two overlapping rectangles?
Atetromino consists of four squares connected along their edges. There are five possible tetromino shapes, I , O , L , T , and S , shown below, which can be rotated or flipped over. Three tetrominoes are used to completely cover a 3×4 rectangle. At least one of the tiles is an S tile. What are the other two tiles?
The region shown below consists of 24 squares, each with side length 1 centimeter. What is the area, in square centimeters, of the largest circle that can fit inside the region, possibly touching the boundaries?
2025 AMC8 #15 · Counting, Probability & Statistics · ★★★
Kei draws a 6 -by- 6 grid. He colors 13 of the unit squares silver and the remaining squares gold. Kei then folds the grid in half vertically, forming pairs of overlapping unit squares. Let m and M equal the least and greatest possible number of gold-on-gold pairs, respectively. What is the value of m+M ?
2025 AMC8 #16 · Counting, Probability & Statistics · ★★★
Five distinct integers from 1 to 10 are chosen, and five distinct integers from 11 to 20 are chosen. No two numbers differ by exactly 10 . What is the sum of the ten chosen numbers?
In the land of Markovia, there are three cities: A , B , and C . There are 100 people who live in A , 120 who live in B , and 160 who live in C . Everyone works in one of the three cities, and a person may work in the same city where they live. In the figure below, an arrow pointing from one city to another is labeled with the fraction of people living in the first city who work in the second city. (For example, 41 of the people who live in A work in B .) How many people work in A ?
The circle shown below on the left has a radius of 1 unit. The region between the circle and the inscribed square is shaded. In the circle shown on the right, one quarter of the region between the circle and the inscribed square is shaded. The shaded regions in the two circles have the same area. What is the radius R , in units, of the circle on the right?
Two towns, A and B , are connected by a straight road that is 15 miles long. Travelling from city A to town B , the speed limit changes every 5 miles: from 25 to 40 to 20 miles per hour (mph). Two cars, one at town A and one at town B , start moving toward each other at the same time. They drive at exactly the speed limit in each portion of the road. How far from town A , in miles, will the two cars meet?
Sarika, Dev, and Rajiv are sharing a large block of cheese. They take turns cutting off half of what remains and eating it: first Sarika eats half of the cheese, then Dev eats half of the remaining half, then Rajiv eats half of what remains, then back to Sarika, and so on. They stop when the cheese is too small to see. About what fraction of the original block of cheese does Sarika eat in total?
2025 AMC8 #21 · Counting, Probability & Statistics · ★★★★
The Konigsberg School has assigned grades 1 through 7 to pods A through G , one grade per pod. Some of the pods are connected by walkways, as shown in the figure below. The school noticed that each pair of connected pods has been assigned grades differing by 1 or more grade levels. (For example, grades 1 and 2 will not be in pods directly connected by a walkway.) What is the sum of the grade levels assigned to pods C, E , and F ?
A classroom has a row of 35 coat hooks. Paulina likes coats to be equally spaced, so that there is the same number of empty hooks before the first coat, after the last coat, and between every coat and the next one. Suppose there is at least 1 coat and at least 1 empty hook. How many different numbers of coats can satisfy Paulina's pattern?
In trapezoid ABCD , angles B and C measure 60∘ and AB = DC . The side lengths are all positive integers, and the perimeter of ABCD is 30 units. How many non-congruent trapezoids satisfy all of these conditions?
2025 AMC8 #25 · Counting, Probability & Statistics · ★★★★★
Makayla finds all the possible ways to draw a path in a 5×5 diamond-shaped grid. Each path starts at the bottom of the grid and ends at the top, always moving one unit northeast or northwest. She computes the area of the region between each path and the right side of the grid. Two examples are shown in the figures below. What is the sum of the areas determined by all possible paths?
Four squares of side length 4, 7, 9, and 10 units are arranged in increasing size order so that their left edges and bottom edges align. The squares alternate in color white-gray-white-gray, respectively, as shown in the figure. What is the area of the visible gray region in square units?
When Yunji added all the integers from 1 through 9, she mistakenly left out a number. Her incorrect sum turned out to be a square number. Which number did Yunji leave out?
2024 AMC8 #5 · Counting, Probability & Statistics · ★★
Aaliyah rolls two standard 6-sided dice. She notices that the product of the two numbers rolled is a multiple of 6. Which of the following integers cannot be the sum of the two numbers?
Sergei skated around an ice rink, gliding along different paths. The gray lines in the figures below show four of the paths labeled P, Q, R, and S. What is the sorted order of the four paths from shortest to longest?
2024 AMC8 #8 · Counting, Probability & Statistics · ★★
On Monday Taye has $2. Every day, he either gains $3 or doubles the amount of money he had on the previous day. How many different dollar amounts could Taye have on Thursday, 3 days later?
All of the marbles in Maria's collection are red, green, or blue. Maria has half as many red marbles as green marbles and twice as many blue marbles as green marbles. Which of the following could be the total number of marbles in Maria's collection?
Rohan keeps a total of 90 guppies in 4 fish tanks.
• There is 1 more guppy in the 2nd tank than in the 1st tank.
• There are 2 more guppies in the 3rd tank than in the 2nd tank.
• There are 3 more guppies in the 4th tank than in the 3rd tank.
2024 AMC8 #16 · Counting, Probability & Statistics · ★★★
Minh enters the numbers 1 through 81 into the cells of a 9 × 9 grid in some order. She calculates the product of the numbers in each row and column. What is the least number of rows and columns that could have a product divisible by 3?
2024 AMC8 #17 · Counting, Probability & Statistics · ★★★
A chess king is said to attack all the squares one step away from it, horizontally, vertically, or diagonally. For instance, a king on the center square of a 3 × 3 grid attacks all 8 other squares, as shown below. Suppose a white king and a black king are placed on different squares of a 3 × 3 grid so that they do not attack each other. In how many ways can this be done?
Three concentric circles centered at O have radii of 1, 2, and 3. Points B and C lie on the largest circle. The region between the two smaller circles is shaded, as is the portion of the region between the two larger circles bounded by central angle ∠BOC, as shown in the figure below. Suppose the shaded and unshaded regions are equal in area. What is the measure of ∠BOC in degrees?
以点 O 为圆心的三个同心圆的半径分别为 1、2、3。点 B 和点 C 位于最大圆上。两个较小圆之间的区域被涂上阴影,两个较大圆之间且位于圆心角 ∠BOC 内的区域也被涂上阴影,如图所示。若阴影区域与非阴影区域面积相等,请问 ∠BOC 的度数是多少?
A group of frogs (called an army) is living in a tree. A frog turns green when in the shade and turns yellow when in the sun. Initially, the ratio of green to yellow frogs was 3:1. Then 3 green frogs moved to the sunny side and 5 yellow frogs moved to the shady side. Now the ratio is 4:1. What is the difference between the number of green frogs and the number of yellow frogs now?
A roll of tape is 4 inches in diameter and is wrapped around a ring that is 2 inches in diameter. A cross section of the tape is shown in the figure below. The tape is 0.015 inches thick. If the tape is completely unrolled, approximately how long would it be? Round your answer to the nearest 100 inches.
Rodrigo has a very large piece of graph paper. First he draws a line segment connecting point (0, 4) to point (2, 0) and colors the 4 cells whose interiors intersect the segment, as shown below. Next Rodrigo draws a line segment connecting point (2000, 3000) to point (5000, 8000). Again he colors the cells whose interiors intersect the segment. How many cells will he color this time?
Jean made a piece of stained glass art in the shape of two mountains, as shown in the figure below.
One mountain peak is 8 feet high and the other peak is 12 feet high. Each peak forms a 90° angle, and the straight sides of the mountains form 45° angles with the ground.
The artwork has an area of 183 square feet. The sides of the mountains meet at an intersection point near the center of the artwork, h feet above the ground.
2024 AMC8 #25 · Counting, Probability & Statistics · ★★★★
A small airplane has 4 rows of seats with 3 seats in each row. Eight passengers have boarded the plane and are distributed randomly among the seats. A married couple is next to board. What is the probability there will be 2 adjacent seats in the same row for the couple?
A square piece of paper is folded twice into four equal quarters, as shown below, then cut along the dashed line. When unfolded, the paper will match which of the following figures?
Wind chill is a measure of how cold people feel when exposed to wind outside. A good estimate for wind chill can be found using this calculation:
(wind chill)=(air temperature)−0.7×(wind speed)
where temperature is measured in degrees Fahrenheit (∘F) and wind speed is measured in miles per hour (mph). Suppose the air temperature is 36∘F and the wind speed is 18 mph. Which of the following is closest to the approximate wind chill?
The numbers from 1 to 49 are arranged in a spiral pattern on a square grid, beginning at the center. The first few numbers have been entered into the grid below. Consider the four numbers that will appear in the shaded squares, on the same diagonal as the number 7. How many of these four numbers are prime?
A lake contains 250 trout, along with a variety of other fish. When a marine biologist catches and releases a sample of 180 fish from the lake, 30 are identified as trout. Assume that the ratio of trout to the total number of fish is the same in both the sample and the lake. How many fish are there in the lake?
A rectangle, with sides parallel to the x-axis and y-axis, has opposite vertices at (15, 3) and (16, 5). A line is drawn through A(0,0) and B(3,1). Another line is drawn through C(0,10) and D(2,9). How many points on the rectangle lie on at least one of the two lines?
2023 AMC8 #8 · Counting, Probability & Statistics · ★★
Lola, Lolo, Tiya, and Tiyo participated in a ping pong tournament. Each player competed against each of the other three players exactly twice. Shown below are the win-loss records for the players. The numbers 1 and 0 represent a win or loss, respectively. For example, Lola won five matches and lost the fourth match. What was Tiyo’s win-loss record?
2023 AMC8 #9 · Counting, Probability & Statistics · ★
Malaika is skiing on a mountain. The graph below shows her elevation, in meters, above the base of the mountain as she skis along a trail. In total, how many seconds does she spend at an elevation between 4 and 7 meters?
Harold made a plum pie to take on a picnic. He was able to eat only 41 of the pie, and he left the rest for his friends. A moose came by and ate 31 of what Harold left behind. After that, a porcupine ate 31 of what the moose left behind. How much of the original pie still remained after the porcupine left?
Harold 做了一个李子派带去野餐。他只吃了这个派的 41,剩下的留给他的朋友们。一只驼鹿经过,吃掉了 Harold 剩下的 31。在那之后,一只豪猪吃掉了驼鹿剩下的派的 31。问豪猪走后,原来的派还剩下多少?
NASA's Perseverance Rover was launched on July 30, 2020. After traveling 292,526,838 miles, it landed on Mars in Jezero Crater about 6.5 months later. Which of the following is closest to the Rover's average interplanetary speed in miles per hour?
The figure below shows a large white circle with a number of smaller white and shaded circles in its interior. What fraction of the interior of the large white circle is shaded?
Along the route of a bicycle race, 7 water stations are evenly spaced between the start and finish lines, as shown in the figure below. There are also 2 repair stations evenly spaced between the start and finish lines. The 3rd water station is located 2 miles after the 1st repair station. How long is the race in miles?
Nicolas is planning to send a package to his friend Anton, who is a stamp collector. To pay for the postage, Nicolas would like to cover the package with a large number of stamps. Suppose he has a collection of 5-cent, 10-cent, and 25-cent stamps, with exactly 20 of each type. What is the greatest number of stamps Nicolas can use to make exactly $7.10 in postage?
(Note: The amount $7.10 corresponds to 7 dollars and 10 cents. One dollar is worth 100 cents.)
Viswam walks half a mile to get to school each day. His route consists of 10 city blocks of equal length and he takes 1 minute to walk each block. Today, after walking 5 blocks, Viswam discovers he has to make a detour, walking 3 blocks of equal length instead of 1 block to reach the next corner. From the time he starts his detour, at what speed, in mph, must he walk in order to get to school at his usual time?
The letters P, Q, and R are entered into a 20×20 table according to the pattern shown below. How many P's, Q's, and R's will appear in the completed table?
A regular octahedron has eight equilateral triangle faces with four faces meeting at each vertex. Jun will make the regular octahedron shown on the right by folding the piece of paper shown on the left. Which numbered face will end up to the right of Q?
Greta Grasshopper sits on a long line of lily pads in a pond. From any lily pad, Greta can jump 5 pads to the right or 3 pads to the left. What is the fewest number of jumps Greta must make to reach the lily pad located 2023 pads to the right of her starting position?
An equilateral triangle is placed inside a larger equilateral triangle so that the region between them can be divided into three congruent trapezoids, as shown below. The side length of the inner triangle is 32 the side length of the larger triangle. What is the ratio of the area of one trapezoid to the area of the inner triangle?
2023 AMC8 #20 · Counting, Probability & Statistics · ★★★
Two integers are inserted into the list 3, 3, 8, 11, 28 to double its range. The mode and median remain unchanged. What is the maximum possible sum of the two additional numbers?
2023 AMC8 #21 · Counting, Probability & Statistics · ★★★★
Alina writes the numbers 1,2,…,9 on separate cards, one number per card. She wishes to divide the cards into 3 groups of 3 cards so that the sum of the numbers in each group will be the same. In how many ways can this be done?
In a sequence of positive integers, each term after the second is the product of the previous two terms. The sixth term is 4000. What is the first term?
2023 AMC8 #23 · Counting, Probability & Statistics · ★★★★
Each square in a 3×3 grid is randomly filled with one of the 4 gray and white tiles shown below on the right. What is the probability that the tiling will contain a large gray diamond in one of the smaller 2×2 grids? Below is an example of such a tiling.
Isosceles triangle ABC has equal side lengths AB and BC. In the figures below, segments are drawn parallel to AC so that the shaded portions of △ABC have the same area. The heights of the two unshaded portions are 11 and 5 units, respectively. What is the height h of △ABC?
The Math Team designed a logo shaped like a multiplication symbol, shown below on a grid of 1-inch squares. What is the area of the logo in square inches?
When three positive integers a, b, and c are multiplied together, their product is $100$. Suppose a < b < c. In how many ways can the numbers be chosen?
Anna and Bella are celebrating their birthdays together. Five years ago, when Bella turned 6 years old, she received a newborn kitten as a birthday present. Today the sum of the ages of the two children and the kitten is 30 years. How many years older than Bella is Anna?
nna 和 Bella 正在一起庆祝她们的生日。五年前,当 Bella 到 6 岁的时候,她收到了一只新生的小猫作为生日礼物。今天,两个孩子与小猫的年龄之和是 30 岁。问 Anna 比 Bella 大多少岁?
Three positive integers are equally spaced on a number line. The middle number is 15, and the largest number is 4 times the smallest number. What is the smallest of these three numbers?
When the World Wide Web first became popular in the 1990 s, download speeds reached a maximum of about 56 kilobits per second. Approximately how many minutes would the download of a 4.2 -megabyte song have taken at that speed? (Note that there are 8000 kilobits in a megabyte.)
A cup of boiling water ( 212∘F ) is placed to cool in a room whose temperature remains constant at 68∘F . Suppose the difference between the water temperature and the room temperature is halved every 5 minutes. What is the water temperature, in degrees Fahrenheit, after 15 minutes?
One sunny day, Ling decided to take a hike in the mountains. She left her house at 8 AM , drove at a constant speed of 45 miles per hour, and arrived at the hiking trail at 10 AM . After hiking for 3 hours, Ling drove home at a constant speed of 60 miles per hour. Which of the following graphs best illustrates the distance between Ling's car and her house over the course of her trip?
Henry the donkey has a very long piece of pasta. He takes a number of bites of pasta, each time eating 3 inches of pasta from the middle of one piece. In the end, he has $10$ pieces of pasta whose total length is 17 inches. How long, in inches, was the piece of pasta he started with?
驴 Henry 有一根很长的面条。他咬了几口面条,每次都是从一段面条的中间吃掉 3 英寸。最后,他还有 10 段面条,总长度为 17 英寸。问他开始吃的时候,那根面条的长度是多少英寸?
2022 AMC8 #12 · Counting, Probability & Statistics · ★★★
The arrows on the two spinners shown below are spun. Let the number N equal 10 times the number on Spinner A, added to the number on Spinner B. What is the probability that N is a perfect square number?
下图所示的两个转盘上的箭头可自由旋转。数 N 等于 10 乘以转盘 A 上箭头所指的数,再加上转盘 B 上箭头所指的数。问 N 是完全平方数的概率是多少?
How many positive integers can fill the blank in the sentence below? “One positive integer is _____ more than twice another, and the sum of the two numbers is 28 .”
2022 AMC8 #15 · Counting, Probability & Statistics · ★★★
Laszlo went online to shop for black pepper and found thirty different black pepper options varying in weight and price, shown in the scatter plot below. In ounces, what is the weight of the pepper that offers the lowest price per ounce?
Four numbers are written in a row. The average of the first two is 21, the average of the middle two is 26, and the average of the last two is 30. What is the average of the first and last of the numbers?
If n is an even positive integer, the double factorial notation n!! represents the product of all the even integers from 2 to n . For example, 8!!=2⋅4⋅6⋅8 . What is the units digit of the following sum? 2!!+4!!+6!!+⋯+2018!!+2020!!+2022!!
如果 n 是一个正整数,那么双阶乘记号 n!!代表从 2 到 n 的所有偶整数的乘积。例如, 8!!=2·4·6·8。问下面和式的个位数字是几?
2!!+4!!+6!!+ … +2018!!+2020!!+2022!!
2022 AMC8 #19 · Counting, Probability & Statistics · ★★★
Mr. Ramos gave a test to his class of 20 students. The dot plot below shows the distribution of test scores. Later Mr. Ramos discovered that there was a scoring error on one of the questions. He regraded the tests, awarding some of the students 5 extra points, which increased the median test score to 85 . What is the minimum number of students who received extra points? (Note that the median test score equals the average of the 2 scores in the middle if the 20 test scores are arranged in increasing order.)
The grid below is to be filled with integers in such a way that the sum of the numbers in each row and the sum of the numbers in each column are the same. Four numbers are missing. The number x in the lower left corner is larger than the other three missing numbers. What is the smallest possible value of x ?
Steph scored 15 baskets out of 20 attempts in the first half of a game, and 10 baskets out of 10 attempts in the second half. Candace took 12 attempts in the first half and 18 attempts in the second. In each half, Steph scored a higher percentage of baskets than Candace. Surprisingly they ended with the same overall percentage of baskets scored. How many more baskets did Candace score in the second half than in the first?
A bus takes 2 minutes to drive from one stop to the next, and waits 1 minute at each stop to let passengers board. Zia takes 5 minutes to walk from one bus stop to the next. As Zia reaches a bus stop, if the bus is at the previous stop or has already left the previous stop, then she will wait for the bus. Otherwise she will start walking toward the next stop. Suppose the bus and Zia start at the same time toward the library, with the bus 3 stops behind. After how many minutes will Zia board the bus?
2022 AMC8 #23 · Counting, Probability & Statistics · ★★★★
A△ or ◯ is placed in each of the nine squares in a 3 -by- 3 grid. Shown below is a sample configuration with three △s in a line. How many configurations will have three △s in a line and three ◯s in a line?
The figure below shows a polygon ABCDEFGH , consisting of rectangles and right triangles. When cut out and folded on the dotted lines, the polygon forms a triangular prism. Suppose that AH = EF = 8 and GH = 14 . What is the volume of the prism?
2022 AMC8 #25 · Counting, Probability & Statistics · ★★★★★
A cricket randomly hops between 4 leaves, on each turn hopping to one of the other 3 leaves with equal probability. After 4 hops what is the probability that the cricket has returned to the leaf where it started?
Luka is making lemonade to sell at a school fundraiser. His recipe requires 4 times as much water as sugar and twice as much sugar as lemon juice. He uses 3 cups of lemon juice. How many cups of water does he need?
Luka 正在做柠檬水,准备在学校的募捐会上出售。他的配料表需要的水是糖的四倍,糖是柠檬汁的两倍。他用了 3 杯柠檬汁。他需要多少杯水?
Four friends do yardwork for their neighbors over the weekend, earning $15, $20, $25, and $40, respectively. They decide to split their earnings equally among themselves. In total, how much will the friend who earned $40 give to the others?
Carrie has a rectangular garden that measures 6 feet by 8 feet. She plants the entire garden with strawberry plants. Carrie is able to plant 4 strawberry plants per square foot, and she harvests an average of 10 strawberries per plant. How many strawberries can she expect to harvest?
Three hexagons of increasing size are shown below. Suppose the dot pattern continues so that each successive hexagon contains one more band of dots. How many dots are in the next hexagonal?
Three fourths of a pitcher is filled with pineapple juice. The pitcher is emptied by pouring an equal amount of juice into each of 5 cups. What percent of the total capacity of the pitcher did each cup receive?
2020 AMC8 #6 · Counting, Probability & Statistics · ★★
Aaron, Darren, Karen, Maren, and Sharon rode on a small train that has five cars that seat one person each. Maren sat in the last car. Aaron sat directly behind Sharon. Darren sat in one of the cars in front of Aaron. At least one person sat between Karen and Darren. Who sat in the middle car?
Ricardo has $2020$ coins, some of which are pennies ( 1 -cent coins) and the rest of which are nickels ( 5 -cent coins). He has at least one penny and at least one nickel. What is the difference in cents between the greatest possible and least amounts of money that Ricardo can have?
Akash's birthday cake is in the form of a 4×4×4 inch cube. The cake has icing on the top and the four side faces, and no icing on the bottom. Suppose the cake is cut into 64 smaller cubes, each measuring 1×1×1 inch, as shown below. How many small pieces will have icing on exactly two sides?
2020 AMC8 #10 · Counting, Probability & Statistics · ★★
Zara has a collection of 4 marbles: an Aggie, a Bumblebee, a Steelie, and a Tiger. She wants to display them in a row on a shelf, but does not want to put the Steelie and the Tiger next to one another. In how many ways can she do this?
After school, Maya and Naomi headed to the beach, 6 miles away. Maya decided to bike while Naomi took a bus. The graph below shows their journeys, indicating the time and distance traveled. What was the difference, in miles per hour, between Naomi's and Maya's average speeds?
For a positive integer n , the factorial notation n! represents the product of the integers from n to 1 . What value of N satisfies the following equation?
5!⋅9!=12⋅N!
对一个正整数 n,符号 n!表示从 n 到 1 的所有整数的乘积。例如, 6!=6·5·4·3·2·3.2·1 则 N 为何值时,满足下面的方程?
Jamal has a drawer containing 6 green socks, 18 purple socks, and 12 orange socks. After adding more purple socks, Jamal noticed that there is now a 60% chance that a sock randomly selected from the drawer is purple. How many purple socks did Jamal add?
2020 AMC8 #14 · Counting, Probability & Statistics · ★★★
There are 20 cities in the County of Newton. Their populations are shown in the bar chart below. The average population of all the cities is indicated by the horizontal dashed line. Which of the following is closest to the total population of all 20 cities?
2020 AMC8 #16 · Counting, Probability & Statistics · ★★★
Each of the points A,B,C,D,E, and F in the figure below represents a different digit from 1 to 6. Each of the five lines shown passes through some of these points. The digits along each line are added to produce five sums, one for each line. The total of the five sums is 47. What is the digit represented by B?
A number is called flippy if its digits alternate between two distinct digits. For example, 2020 and 37373 are flippy, but 3883 and 123123 are not. How many five-digit flippy numbers are divisible by $15?$
A scientist walking through a forest recorded as integers the heights of 5 trees standing in a row. She observed that each tree was either 2 times as tall or half as tall as the one to its right. Unfortunately some of her data was lost when rain fell on her notebook. Her notes are shown below, with blanks indicating the missing numbers. Based on her observations, the scientist was able to reconstruct the lost data. What was the average height of the trees, in meters?
2020 AMC8 #21 · Counting, Probability & Statistics · ★★★
A game board consists of 64 squares that alternate in color between black and white. The figure below shows square P in the bottom row and square Q in the top row. A marker is placed at P. A step consists of moving the marker onto one of the adjoining white squares in the row above. How many 7 -step paths are there from P to Q? (The figure shows a sample path.)
一种游戏板由 64 个黑白相间的方块组成。下图显示了底行中的一个正方形 P 和顶行中的一个正方形 Q。在正方形 P 上放了一个标记,将标记移到上面一行中相邻的一个白色正方形上,这个操作称为一步。从 P 到 Q 有多少种 7 步路径?(图中显示了一种可能的示例路径)。
When a positive integer N is fed into a machine, the output is a number calculated according to the rule shown below. For example, starting with an input of N = 7, the machine will output 3⋅7+1=22. Then if the output is repeatedly inserted into the machine five more times, the final output is 26: 7→22→11→34→17→52→26. When the same 6-step process is applied to a different starting value of N, the final output is $1$. What is the sum of all such integers N?
2020 AMC8 #23 · Counting, Probability & Statistics · ★★★★
Five different awards are to be given to three students. Each student will receive at least one award. In how many different ways can the awards be distributed?
A large square region is paved with n^2 gray square tiles, each measuring s inches on a side. A border d inches wide surrounds each tile. The figure below shows the case for n=3 . When n=24 , the 576 gray tiles cover 64% of the area of the large square region. What is the ratio sd for this larger value of n?
一个大正方形区域用 n2 块灰色方形瓷砖铺成,每块边长为 s 英寸。每块瓷砖四周都有宽 d 英寸的边框。下图为 n=3 的情形。当 n=24 时,576 块灰色瓷砖覆盖了大正方形面积的 64%。那么对于这个较大的 n 值,sd 的比值是多少?
Rectangles R_1 and R_2, and squares S_1, S_2, and S_3, shown below, combine to form a rectangle that is 3322 units wide and 2020 units high. What is the side length of S_2 in units?
Ike and Mike go into a sandwich shop with a total of $30.00 to spend. Sandwiches cost $4.50 each and soft drinks cost $1.00 each. Ike and Mike plan to buy as many sandwiches as they can, and use any remaining money to buy soft drinks. Counting both sandwiches and soft drinks, how many items will they buy?
Ike 和 Mike 带着总共 30 美元去一家三明治商店,每块三明治价格 4.5 美元,每瓶软饮价格 1 美元。Ike 和 Mike 打算尽可能多的买三明治,然后用剩下的钱去买软饮料,那么三明治和软饮总个数加起来,他们将买多少件物品?
Three identical rectangles are put together to form rectangle ABCD , as shown in the figure below. Given that the length of the shorter side of each of the rectangles is 5 feet, what is the area in square feet of rectangle ABCD ?
A tortoise challenges a hare to a race. The hare eagerly agrees and quickly runs ahead, leaving the slow-moving tortoise behind. Confident that he will win, the hare stops to take a nap. Meanwhile, the tortoise walks at a slow steady pace for the entire race. The hare awakes and runs to the finish line, only to find the tortoise already there. Which of the following graphs matches the description of the race, showing the distance d traveled by the two animals over time t from start to finish?
乌龟向野兔发起挑战赛跑,野兔开心的同意了,然后迅速跑到了前面,把行动迟缓的乌龟甩在了后面,野兔很自信自己会赢,于是停下来打了个盹,同时,乌龟以缓慢但恒定的速度走完了全程。野兔醒了,当它跑到终点时,发现乌龟已经在那里了。下面哪张图和上述对比赛的描述相匹配,并正确的展示了这 2 只动物走过的距离 d 与从开始到结束这段时间 t 的关系?
2019 AMC8 #6 · Counting, Probability & Statistics · ★★
There are 81 grid points (uniformly spaced) in the square shown in the diagram below, including the points on the edges. Point P is in the center of the square. Given that point Q is randomly chosen among the other 80 points, what is the probability that the line PQ is a line of symmetry for the square?
2019 AMC8 #7 · Counting, Probability & Statistics · ★★
Shauna takes five tests, each worth a maximum of 100 points. Her scores on the first three tests are 76 , 94 , and 87 . In order to average 81 for all five tests, what is the lowest score she could earn on one of the other two tests?
Gilda has a bag of marbles. She gives 20% of them to her friend Pedro. Then Gilda gives 10% of what is left to another friend, Ebony. Finally, Gilda gives 25% of what is now left in the bag to her brother Jimmy. What percentage of her original bag of marbles does Gilda have left for herself?
Alex and Felicia each have cats as pets. Alex buys cat food in cylindrical cans that are 6 cm in diameter and 12 cm high. Felicia buys cat food in cylindrical cans that are 12 cm in diameter and 6 cm high. What is the ratio of the volume of one of Alex's cans to the volume of one of Felicia's cans?
Alex 和 Felicia 他们都有宠物猫。Alex 买的宠物猫粮是装在底面直径为 6 厘米,高度 12 厘米的圆柱形罐子里的。Felicia 买的猫粮则装在底面直径是 12 厘米,高为 6 厘米的圆柱形罐子里。问 Alex 的罐子的体积和 Felicia 的罐子的体积之比是多少?
2019 AMC8 #10 · Counting, Probability & Statistics · ★★
The diagram shows the number of students at soccer practice each weekday during last week. After computing the mean and median values, Coach discovers that there were actually 21 participants on Wednesday. Which of the following statements describes the change in the mean and median after the correction is made?
2019 AMC8 #11 · Counting, Probability & Statistics · ★★★
The eighth grade class at Lincoln Middle School has $93$ students. Each student takes a math class or a foreign language class or both. There are 70 eighth graders taking a math class, and there are 54 eighth graders taking a foreign language class. How many eighth graders take only a math class and not a foreign language class?
The faces of a cube are painted in six different colors: red (R) , white (W) , green (G) , brown (B) , aqua (A) , and purple (P) . Three views of the cube are shown below. What is the color of the face opposite the aqua face?
A palindrome is a number that has the same value when read from left to right or from right to left. (For example, 12321 is a palindrome.) Let N be the least three-digit integer which is not a palindrome but which is the sum of three distinct two-digit palindromes. What is the sum of the digits of N ?
回环数是指从左向右读和从右向左读,读数是一样的数(例如,12321 是个回环数)。N 是满足以下条件的最小三位整数:它不是个回环数,并且它是 3 个不同的两位回环数的和。问 N 的各个位上的数字之和是多少?
Isabella has $6$ coupons that can be redeemed for free ice cream cones at Pete's Sweet Treats. In order to make the coupons last, she decides that she will redeem one every 10 days until she has used them all. She knows that Pete's is closed on Sundays, but as she circles the 6 dates on her calendar, she realizes that no circled date falls on a Sunday. On what day of the week does Isabella redeem her first coupon?
Isabella 有 6 张优惠券,可用于在 Pete 甜品店里免费兑换冰激凌。为了最后使用优惠券,她决定每 10 天兑换一次直到所有的优惠券都使用完毕。已知 Pete 甜品店周日是不营业的,当她在日历上圈出兑换冰激凌的这 6 天时,发现没有哪天是周日。问 Isabella 兑换她的第一个优惠券是在周几?
2019 AMC8 #15 · Counting, Probability & Statistics · ★★★
On a beach, 50 people are wearing sunglasses and 35 people are wearing caps. Some people are wearing both sunglasses and caps. If one of the people wearing a cap is selected at random, the probability that this person is also wearing sunglasses is 52 . If instead, someone wearing sunglasses is selected at random, what is the probability that this person is also wearing a cap?
Qiang drives 15 miles at an average speed of 30 miles per hour. How many additional miles will he have to drive at 55 miles per hour to average 50 miles per hour for the entire trip?
2019 AMC8 #18 · Counting, Probability & Statistics · ★★★
The faces of each of two fair dice are numbered 1 , 2 , 3 , 5 , 7 , and 8 . When the two dice are tossed, what is the probability that their sum will be an even number?
2019 AMC8 #19 · Counting, Probability & Statistics · ★★★
In a tournament there are six teams that play each other twice. A team earns $3$ points for a win, 1 point for a draw, and 0 points for a loss. After all the games have been played it turns out that the top three teams earned the same number of total points. What is the greatest possible number of total points for each of the top three teams?
A store increased the original price of a shirt by a certain percent and then lowered the new price by the same amount. Given that the resulting price was 84% of the original price, by what percent was the price increased and decreased?
After Euclid High School's last basketball game, it was determined that 41 of the team's points were scored by Alexa and 72 were scored by Brittany. Chelsea scored 15 points. None of the other 7 team members scored more than 2 points. What was the total number of points scored by the other 7 team members?
In triangle ABC , point D divides side AC so that AD:DC=1:2 . Let E be the midpoint of BD and let F be the point of intersection of line BC and line AE . Given that the area of △ABC is 360 , what is the area of △EBF?
在三角形 ABC 中,点 D 把边分成的两段满足 AD:DC=1:2,点 E 是线段 BD 的中点,F 是直线 BC 和 AE 的交点。已知 ΔABC 的面积是 360,问 ΔEBF 的面积是多少?
An amusement park has a collection of scale models, with a ratio of 1:20 , of buildings and other sights from around the country. The height of the United States Capitol is 289 feet. What is the height in feet of its duplicate to the nearest whole number?
2018 AMC8 #3 · Counting, Probability & Statistics · ★★
Students Arn, Bob, Cyd, Dan, Eve, and Fon are arranged in that order in a circle. They start counting: Arn first, then Bob, and so forth. When the number contains a 7 as a digit (such as 47) or is a multiple of 7 that person leaves the circle and the counting continues. Who is the last one present in the circle?
Arn,Bob,Cyd,Dan,Eve 和 Fon 以这样的顺序围成一圈。他们开始数数:Arn 先开始,然后 Bob,以此类推。当数包含数字 7(例如 47)或者是 7 的倍数时,那个人就离开圆圈,数数继续进行。最后一个离开圆圈的是谁?
On a trip to the beach, Anh traveled 50 miles on the highway and 10 miles on a coastal access road. He drove three times as fast on the highway as on the coastal road. If Anh spent 30 minutes driving on the coastal road, how many minutes did his entire trip take?
2018 AMC8 #8 · Counting, Probability & Statistics · ★★
Mr. Garcia asked the members of his health class how many days last week they exercised for at least 30 minutes. The results are summarized in the following bar graph, where the heights of the bars represent the number of students. What was the mean number of days of exercise last week, rounded to the nearest hundredth, reported by the students in Mr. Garcia's class?
Tyler is tiling the floor of his 12-foot by 16-foot living room. He plans to place one-foot by one-foot square tiles to form a border along the edges of the room and to fill in the rest of the floor with two-foot by two-foot square tiles. How many tiles will he use?
The harmonic mean of a set of non-zero numbers is the reciprocal of the average of the reciprocals of the numbers. What is the harmonic mean of 1, 2, and 4?
2018 AMC8 #11 · Counting, Probability & Statistics · ★★★
Abby, Bridget, and four of their classmates will be seated in two rows of three for a group picture, as shown. If the seating positions are assigned randomly, what is the probability that Abby and Bridget are adjacent to each other in the same row or the same column?
The clock in Sri's car, which is not accurate, gains time at a constant rate. One day as he begins shopping, he notes that his car clock and his watch (which is accurate) both say 12:00 noon. When he is done shopping, his watch says 12:30 and his car clock says 12:35. Later that day, Sri loses his watch. He looks at his car clock and it says 7:00. What is the actual time?
Lalia took five math tests, each worth a maximum of 100 points. Laila's score on each test was an integer between 0 and 100, inclusive. Laila received the same score on the first four tests, and she received a higher score on the last test. Her average score on the five tests was 82. How many values are possible for Laila's score on the last test?
In the diagram below, a diameter of each of the two smaller circles is a radius of the larger circle. If the two smaller circles have a combined area of 1 square unit, then what is the area of the shaded region, in square units?
2018 AMC8 #16 · Counting, Probability & Statistics · ★★★
Professor Chang has nine different language books lined up on a bookshelf: two Arabic, three German, and four Spanish. How many ways are there to arrange the nine books on the shelf keeping the Arabic books together and keeping the Spanish books together?
Bella begins to walk from her house toward her friend Ella's house. At the same time, Ella begins to ride her bicycle toward Bella's house. They each maintain a constant speed, and Ella rides 5 times as fast as Bella walks. The distance between their houses is 2 miles, which is 10,560 feet, and Bella covers 221 feet with each step. How many steps will Bella take by the time she meets Ella?
Bella 开始从她家步行去她朋友 Ella 的家。同时,Ella 骑着自行车开始向 Bella 的家出发。她们均保持各自恒定的速度,并且 Ella 骑车的速度是 Bella 行走速度的 5 倍。她们家相距 2 英里,即 10,560 英尺,已知 Bella 每步长为 221 英尺,那么当 Bella 和 Ella 相遇时,Bella 走了多少步?
2018 AMC8 #19 · Counting, Probability & Statistics · ★★★
In a sign pyramid a cell gets a "+" if the two cells below it have the same sign, and it gets a "-" if the two cells below it have different signs. The diagram below illustrates a sign pyramid with four levels. How many possible ways are there to fill the four cells in the bottom row to produce a "+" at the top of the pyramid?
In △ABC, a point E is on AB with AE=1 and EB=2. Point D is on AC so that DE∥BC and point F is on BC so that EF∥AC. What is the ratio of the area of CDEF to the area of △ABC?
在 △ABC 中,点 E 在边 AB 上,满足 AE=1,EB=2。点 D 在边 AC 上,满足 DE∥BC;点 F 在边 BC 上,满足 EF∥AC。则 CDEF 的面积与 △ABC 的面积之比是多少?
How many positive three-digit integers have a remainder of 2 when divided by 6, a remainder of 5 when divided by 9, and a remainder of 7 when divided by 11?
2018 AMC8 #23 · Counting, Probability & Statistics · ★★★★
From a regular octagon, a triangle is formed by connecting three randomly chosen vertices of the octagon. What is the probability that at least one of the sides of the triangle is also a side of the octagon?
In the cube ABCDEFGH with opposite vertices C and E, J and I are the midpoints of edges FB and HD, respectively. Let R be the ratio of the area of the cross-section EJCI to the area of one of the faces of the cube. What is R2?
在正方体 ABCDEFGH 中,顶点 C 和 E 相对,点 J 和点 I 分别是棱 FB 和 HD 的中点。R 表示横截面 EJCI 的面积和正方体的一个面的面积之比,求 R2。
2017 AMC8 #2 · Counting, Probability & Statistics · ★
Alicia, Brenda, and Colby were the candidates in a recent election for student president. The pie chart below shows how the votes were distributed among the three candidates. If Brenda received 36 votes, then how many votes were cast all together?
Let Z be a 6-digit positive integer, such as 247247, whose first three digits are the same as its last three digits taken in the same order. Which of the following numbers must also be a factor of Z ?
Z 表示一个 6 位的正整数,例如 247247,从左往右前三位数字和后三位的数字一样。下面哪个数一定也是 Z 的一个因子?
Malcolm wants to visit Isabella after school today and knows the street where she lives but doesn't know her house number. She tells him, "My house number has two digits, and exactly three of the following four statements about it are true." (1) It is prime. (2) It is even. (3) It is divisible by 7. (4) One of its digits is 9. This information allows Malcolm to determine Isabella's house number. What is its units digit?
All of Marcy's marbles are blue, red, green, or yellow. One third of her marbles are blue, one fourth of them are red, and six of them are green. What is the smallest number of yellow marbles that Marcy could have?
2017 AMC8 #10 · Counting, Probability & Statistics · ★★
A box contains five cards, numbered 1, 2, 3, 4, and 5. Three cards are selected randomly without replacement from the box. What is the probability that 4 is the largest value selected?
A square-shaped floor is covered with congruent square tiles. If the total number of tiles that lie on the two diagonals is 37, how many tiles cover the floor?
The smallest positive integer greater than 1 that leaves a remainder of 1 when divided by 4, 5, and 6 lies between which of the following pairs of numbers?
2017 AMC8 #13 · Counting, Probability & Statistics · ★★★
Peter, Emma, and Kyler played chess with each other. Peter won 4 games and lost 2 games. Emma won 3 games and lost 3 games. If Kyler lost 3 games, how many games did he win?
Chloe and Zoe are both students in Ms. Demeanor's math class. Last night, they each solved half of the problems in their homework assignment alone and then solved the other half together. Chloe had correct answers to only 80% of the problems she solved alone, but overall 88% of her answers were correct. Zoe had correct answers to 90% of the problems she solved alone. What was Zoe's overall percentage of correct answers?
2017 AMC8 #15 · Counting, Probability & Statistics · ★★★
In the arrangement of letters and numerals below, by how many different paths can one spell AMC8? Beginning at the A in the middle, a path allows only moves from one letter to an adjacent (above, below, left, or right, but not diagonal) letter. One example of such a path is traced in the picture.
在下图所示的字母和数字的排布中,拼写出 AMC8 有多少种方法?要求从中间的 A 开始,移动的路径只允许从一个字母移到和这个字母相邻的字母(上,下,左,右,但不允许是对角线)。一种可能的路径标示在图中。
Starting with some gold coins and some empty treasure chests, I tried to put 9 gold coins in each treasure chest, but that left 2 treasure chests empty. So instead I put 6 gold coins in each treasure chest, but then I had $3$ gold coins left over. How many gold coins did I have?
For any positive integer M , the notation M! denotes the product of the integers 1 through M . What is the largest integer n for which 5n is a factor of the sum 98!+99!+100! ?
对于任何正整数 M 来说,符号 M!表示从 1 到 M 的所有整数的乘积。使得 +100!的一个因子的最大整数 n 是多少?
In the right triangle ABC , AC=12 , BC=5 , and angle C is a right angle. A semicircle is inscribed in the triangle as shown. What is the radius of the semicircle?
在直角三角形 ABC 中,AC=12,BC=5,且角 C 是个直角。一个半圆如下图所示内切于三角形中,那么这个半圆的半径是多少?
Each day for four days, Linda traveled for one hour at a speed that resulted in her traveling one mile in an integer number of minutes. Each day after the first, her speed decreased so that the number of minutes to travel one mile increased by 5 minutes over the preceding day. Each of the four days, her distance traveled was also an integer number of miles. What was the total number of miles for the four trips?
2017 AMC8 #24 · Counting, Probability & Statistics · ★★★★
Mrs. Sanders has three grandchildren, who call her regularly. One calls her every three days, one calls her every four days, and one calls her every five days. All three called her on December 31, 2016. On how many days during the next year did she not receive a phone call from any of her grandchildren?
In the figure shown, US and UT are line segments each of length 2, and m∠TUS=60∘. Arcs TR⌢ and SR⌢ are each one-sixth of a circle with radius 2. What is the area of the region shown?
When Cheenu was a boy, he could run 15 miles in 3 hours and 30 minutes. As an old man, he can now walk 10 miles in 4 hours. How many minutes longer does it take for him to walk a mile now compared to when he was a boy?
The number N is a two-digit number. • When N is divided by 9, the remainder is 1. • When N is divided by 10, the remainder is 3. What is the remainder when N is divided by 11?
N 是个两位数。
·当 N 除以 9,余数为 1. ·当 N 除以 10,余数为 3. 当 N 除以 11 时,余数是多少?
Determine how many two-digit numbers satisfy the following property: when the number is added to the number obtained by reversing its digits, the sum is 132.
Jefferson Middle School has the same number of boys and girls. 43 of the girls and 32 of the boys went on a field trip. What fraction of the students on the field trip were girls?
Jefferson 中学的男生和女生数目相同。 的女生和 的男生去郊游。那么这些去郊游的学生中,有多少比例是女生?
Karl's car uses a gallon of gas every 35 miles, and his gas tank holds 14 gallons when it is full. One day, Karl started with a full tank of gas, drove 350 miles, bought 8 gallons of gas, and continued driving to his destination. When he arrived, his gas tank was half full. How many miles did Karl drive that day?
Karl 的汽车每开 35 英里就需要 1 加仑汽油,且当他的油缸加满时,可以装 14 加仑的汽油。
一天,Karl 开始他的行程前,把油缸加满了汽油,接着开了 350 英里,之后买了 8 加仑汽油,然后继续开到目的地。当他到达目的地时,他的油缸只剩下一半汽油。问 Karl 那天总共开了多少英里?
Annie and Bonnie are running laps around a 400 -meter oval track. They started together, but Annie has pulled ahead, because she runs 25% faster than Bonnie. How many laps will Annie have run when she first passes Bonnie?
2016 AMC8 #17 · Counting, Probability & Statistics · ★★★
An ATM password at Fred's Bank is composed of four digits from 0 to 9 , with repeated digits allowable. If no password may begin with the sequence 9,1,1, then how many passwords are possible?
Fred 银行的取款机密码由 0 到 9 中的 4 个数字组成,且允许重复,如果密码不允许以序列 9,1,1 开头,那么一共有多少种可能的密码?
2016 AMC8 #18 · Counting, Probability & Statistics · ★★★
In an All-Area track meet, 216 sprinters enter a 100- meter dash competition. The track has $6$ lanes, so only 6 sprinters can compete at a time. At the end of each race, the five non-winners are eliminated, and the winner will compete again in a later race. How many races are needed to determine the champion sprinter?
The least common multiple of a and b is 12 , and the least common multiple of b and c is 15 . What is the least possible value of the least common multiple of a and c ?
a 和 b 的最小公倍数是 12,b 和 c 的最小公倍数是 15,问 a 和 c 的最小公倍数的最小可能值是多少?
2016 AMC8 #21 · Counting, Probability & Statistics · ★★★★
A top hat contains 3 red chips and 2 green chips. Chips are drawn randomly, one at a time without replacement, until all 3 of the reds are drawn or until both green chips are drawn. What is the probability that the 3 reds are drawn?
Two congruent circles centered at points A and B each pass through the other circle's center. The line containing both A and B is extended to intersect the circles at points C and D . The circles intersect at two points, one of which is E . What is the degree measure of ∠CED ?
两个圆心分别在点 A 和点 B 的全等圆各自通过对方的圆心。连接点 A 和点 B 的直线和这 2 个圆交于点 C 和点 D。这 2 个圆交于 2 个点,其中之一是点 E.那么的度数是多少?
The digits 1 , 2 , 3 , 4 , and 5 are each used once to write a five-digit number PQRST . The three-digit number PQR is divisible by 4 , the three-digit number QRS is divisible by 5 , and the three-digit number RST is divisible by 3 . What is P ?
A semicircle is inscribed in an isosceles triangle with base 16 and height 15 so that the diameter of the semicircle is contained in the base of the triangle as shown. What is the radius of the semicircle?
Onkon wants to cover his room's floor with his favourite red carpet. How many square yards of red carpet are required to cover a rectangular floor that is 12 feet long and 9 feet wide? (There are 3 feet in a yard.)
Jack and Jill are going swimming at a pool that is one mile from their house. They leave home simultaneously. Jill rides her bicycle to the pool at a constant speed of 10 miles per hour. Jack walks to the pool at a constant speed of 4 miles per hour. How many minutes before Jack does Jill arrive?
Jack 和 Jill 要去距离他们家 1 英里的游泳池去游泳。他们同时从家出发。Jill 以 10 英里每小时的速度骑车去泳池,Jack 以 4 英里每小时的速度走过去。那么 Jill 比 Jack 早到多少分钟?
2015 AMC8 #4 · Counting, Probability & Statistics · ★
The Centerville Middle School chess team consists of two boys and three girls. A photographer wants to take a picture of the team to appear in the local newspaper. She decides to have them sit in a row with a boy at each end and the three girls in the middle. How many such arrangements are possible?
2015 AMC8 #7 · Counting, Probability & Statistics · ★★
Each of two boxes contains three chips numbered 1 , 2 , 3 . A chip is drawn randomly from each box and the numbers on the two chips are multiplied. What is the probability that their product is even?
On her first day of work, Janabel sold one widget. On day two, she sold three widgets. On day three, she sold five widgets, and on each succeeding day, she sold two more widgets than she had sold on the previous day. How many widgets in total had Janabel sold after working 20 days?
2015 AMC8 #11 · Counting, Probability & Statistics · ★★★
In the small country of Mathland, all automobile license plates have four symbols. The first must be a vowel (A, E, I, O, or U), the second and third must be two different letters among the 21 non-vowels, and the fourth must be a digit (0 through 9). If the symbols are chosen at random subject to these conditions, what is the probability that the plate will read "AMC8"?
2015 AMC8 #15 · Counting, Probability & Statistics · ★★★
At Euler Middle School, 198 students voted on two issues in a school referendum with the following results: 149 voted in favor of the first issue and 119 voted in favor of the second issue. If there were exactly 29 students who voted against both issues, how many students voted in favor of both issues?
In a middle-school mentoring program, a number of the sixth graders are paired with a ninth-grade student as a buddy. No ninth grader is assigned more than one sixth-grade buddy. If 31 of all the ninth graders are paired with 52 of all the sixth graders, what fraction of the total number of sixth and ninth graders have a buddy?
Jeremy's father drives him to school in rush hour traffic in 20 minutes. One day there is no traffic, so his father can drive him 18 miles per hour faster and gets him to school in 12 minutes. How far in miles is it to school?
Jeremy 的爸爸在交通高峰期把他送到学校需要 20 分钟。这一天路上车不多,因此他爸爸开车的速度提高了 18 英里每小时,把他送到学校花了 12 分钟,那么从他家到学校的距离有多少英里?
An arithmetic sequence is a sequence in which each term after the first is obtained by adding a constant to the previous term. For example, 2,5,8,11,14 is an arithmetic sequence with five terms, in which the first term is 2 and the constant added is 3 . Each row and each column in this 5×5 array is an arithmetic sequence with five terms. The square in the center is labelled X as shown. What is the value of X ?
Ralph went to the store and bought 12 pairs of socks for a total of $24 . Some of the socks he bought cost $1 a pair, some of the socks he bought cost $3 a pair, and some of the socks he bought cost $4 a pair. If he bought at least one pair of each type, how many pairs of $1 socks did Ralph buy?
In the given figure hexagon ABCDEF is equiangular, ABJI and FEHG are squares with areas 18 and 32 respectively, △JBK is equilateral and FE=BC . What is the area of △KBC?
On June 1, a group of students is standing in rows, with 15 students in each row. On June 2, the same group is standing with all of the students in one long row. On June 3, the same group is standing with just one student in each row. On June 4, the same group is standing with 6 students in each row. This process continues through June 12 with a different number of students per row each day. However, on June 13, they cannot find a new way of organizing the students. What is the smallest possible number of students in the group?
2015 AMC8 #23 · Counting, Probability & Statistics · ★★★★
Tom has twelve slips of paper which he wants to put into five cups labeled A , B , C , D , E . He wants the sum of the numbers on the slips in each cup to be an integer. Furthermore, he wants the five integers to be consecutive and increasing from A to E . The numbers on the papers are 2, 2, 2, 2.5, 2.5, 3, 3, 3, 3, 3.5, 4, and 4.5 . If a slip with 2 goes into cup E and a slip with 3 goes into cup B , then the slip with 3.5 must go into what cup?
Tom 想把 12 张纸条放进 5 个标有 A,B,C,D,E 的杯子中。他希望每个杯子中的纸条上的数字之和均为整数。并且,他希望这 5 个整数是连续的整数,从 A 到 E 递增。这 12 张纸条上的数字分别是 2,2,2,2.5,2.5,3,3,3,3,3.5,4,4.5.如果写有 2 的那张纸条放进了杯子 E,写有 3 的那张纸条放进了杯子 B,那么写有 3.5 的那张纸一定放进了哪个杯子?
A baseball league consists of two four-team divisions. Each team plays every other team in its division N games. Each team plays every team in the other division M games with N>2M and M>4 . Each team plays a 76 game schedule. How many games does a team play within its own division?
一个棒球联盟有两组组成,每组 4 支队伍。每组里面的每支队伍和自己组内的其他每支队伍都打 N 场比赛。每支队伍和另一组的每支队伍都打 M 场比赛,且 N>2M,M>4,每支队伍共需要打 76 场比赛,那么每支队伍和自己组内的队伍共需要打多少场比赛?
One-inch squares are cut from the corners of this 5 inch square. What is the area in square inches of the largest square that can fit into the remaining space?
Harry and Terry are each told to calculate 8-(2+5) . Harry gets the correct answer. Terry ignores the parentheses and calculates 8-2+5 . If Harry's answer is H and Terry's answer is T , what is H-T ?
Harry 和 Terry 都被要求计算 $8-(2+5)$。Harry 算对了,而 Terry 忽略了括号,计算的是 8-2+5。若 Harry 的答案是 H,Terry 的答案是 T,那么 H-T 是多少?
Paul owes Paula 35 cents and has a pocket full of 5-cent coins, 10-cent coins, and 25-cent coins that he can use to pay her. What is the difference between the largest and the smallest number of coins he can use to pay her?
Paul 欠了 Paula 35 美分。Paula 目前口袋里有一堆 5 美分,10 美分和 25 美分的硬币可以用来还钱,他可用于还钱的最多硬币数目和最少硬币数目的差是多少?
Isabella had a week to read a book for a school assignment. She read an average of 36 pages per day for the first three days and an average of 44 pages per day for the next three days. She then finished the book by reading 10 pages on the last day. How many pages were in the book?
Eleven members of the Middle School Math Club each paid the same amount for a guest speaker to talk about problem solving at their math club meeting. They paid their guest speaker $1A2 . What is the missing digit A of this 3 -digit number?
中学数学俱乐部的 11 个成员为了邀请一个客座演讲人在他们的数学俱乐部会议上讲授解题技巧,每个人都支付了同样的美元金额数且这个数是个整数。他们总共支付给客座演讲人,这个三位数中的 A 代表什么数字?
The first AMC 8 was given in 1985 and it has been given annually since that time. Samantha turned 12 years old the year that she took the seventh AMC 8 . In what year was Samantha born?
2014 AMC8 #11 · Counting, Probability & Statistics · ★★★
Jack wants to bike from his house to Jill's house, which is located three blocks east and two blocks north of Jack's house. After biking each block, Jack can continue either east or north, but he needs to avoid a dangerous intersection one block east and one block north of his house. In how many ways can he reach Jill's house by biking a total of five blocks?
Jack 想从他家骑车到 Jill 家去,Jill 家位于 Jack 家向东 3 个街区,向北 2 个街区的位置。当 Jack 骑车经过每个街区后,他可以选择继续向东或者向北,但他必须绕开离他家向东 1 个街区,向北 1 个街区的一个危险的十字路口。那么他经过 5 个街区骑车到 Jill 的家一共有多少种路线?
2014 AMC8 #12 · Counting, Probability & Statistics · ★★★
A magazine printed photos of three celebrities along with three photos of the celebrities as babies. The baby pictures did not identify the celebrities. Readers were asked to match each celebrity with the correct baby pictures. What is the probability that a reader guessing at random will match all three correctly?
The circumference of the circle with center O is divided into 12 equal arcs, marked the letters A through L as seen below. What is the number of degrees in the sum of the angles x and y ?
如下图所示,圆心为 O 的圆被分成 12 个相等的圆弧,由字母 A 到 L 标识。那么角 x 和角 y 的度数之和是多少?
2014 AMC8 #16 · Counting, Probability & Statistics · ★★★
The "Middle School Eight" basketball conference has $8$ teams. Every season, each team plays every other conference team twice (home and away), and each team also plays 4 games against non-conference opponents. What is the total number of games in a season involving the "Middle School eight" teams?
George walks 1 mile to school. He leaves home at the same time each day, walks at a steady speed of 3 miles per hour, and arrives just as school begins. Today he was distracted by the pleasant weather and walked the first 21 mile at a speed of only 2 miles per hour. At how many miles per hour must George run the last 21 mile in order to arrive just as school begins today?
George 每天同一时间以恒定的 3 英里每小时的速度从家步行 1 英里去学校,且恰好准时到校。今天他被好天气吸引,因此前 英里路程的速度仅为 2 英里每小时。那么后面 英里的路程他应该以多少英里每小时的速度奔跑才能准时到校?
2014 AMC8 #18 · Counting, Probability & Statistics · ★★★
Four children were born at City Hospital yesterday. Assume each child is equally likely to be a boy or a girl. Which of the following outcomes is most likely?
A cube with 3-inch edges is to be constructed from 27 smaller cubes with 1-inch edges. Twenty-one of the cubes are colored red and 6 are colored white. If the 3-inch cube is constructed to have the smallest possible white surface area showing, what fraction of the surface area is white?
Rectangle ABCD has sides CD=3 and DA=5 . A circle with a radius of 1 is centered at A , a circle with a radius of 2 is centered at B , and a circle with a radius of 3 is centered at C . Which of the following is closest to the area of the region inside the rectangle but outside all three circles?
长方形 ABCD 的边长 CD=3,DA=5.圆 A 的半径为 1,圆 B 的半径为 2,圆 C 的半径为
3.那么在长方形内部但在三个圆外部的区域的面积最接近下面哪个数?
Three members of the Euclid Middle School girls' softball team had the following conversation. Ashley: I just realized that our uniform numbers are all 2 -digit primes. Bethany : And the sum of your two uniform numbers is the date of my birthday earlier this month. Caitlin: That's funny. The sum of your two uniform numbers is the date of my birthday later this month. Ashley: And the sum of your two uniform numbers is today's date. What number does Caitlin wear?
2014 AMC8 #24 · Counting, Probability & Statistics · ★★★★
One day the Beverage Barn sold 252 cans of soda to 100 customers, and every customer bought at least one can of soda. What is the maximum possible median number of cans of soda bought per customer on that day?
一天 Beverage Barn 向 100 个顾客卖出了 252 罐苏打水,且每个顾客买了至少一罐苏打水。
那么那天每个顾客所买苏打水的罐数的中位数最大可能是多少?
A straight one-mile stretch of highway, 40 feet wide, is closed. Robert rides his bike on a path composed of semicircles as shown. If he rides at 5 miles per hour, how many hours will it take to cover the one-mile stretch? Note: 1 mile = 5280 feet
Danica wants to arrange her model cars in rows with exactly 6 cars in each row. She now has 23 model cars. What is the smallest number of additional cars she must buy in order to be able to arrange all her cars this way?
A sign at the fish market says, "50 % off, today only: half-pound packages for just $3 per package." What is the regular price for a full pound of fish, in dollars?
Eight friends ate at a restaurant and agreed to share the bill equally. Because Judi forgot her money, each of her seven friends paid an extra $2.50 to cover her portion of the total bill. What was the total bill?
2013 AMC8 #5 · Counting, Probability & Statistics · ★
Hammie is in 6th grade and weighs 106 pounds. His quadruplet sisters are tiny babies and weigh 5, 5, 6, and 8 pounds. Which is greater, the average (mean) weight of these five children or the median weight, and by how many pounds?
The number in each box below is the product of the numbers in the two boxes that touch it in the row above. For example, 30=6×5. What is the missing number in the top row?
Trey and his mom stopped at a railroad crossing to let a train pass. As the train began to pass, Trey counted 6 cars in the first 10 seconds. It took the train 2 minutes and 45 seconds to clear the crossing at a constant speed. Which of the following was the most likely number of cars in the train?
The Incredible Hulk can double the distance he jumps with each succeeding jump. If his first jump is 1 meter, the second jump is 2 meters, the third jump is 4 meters, and so on, then on which jump will he first be able to jump more than 1 kilometer (1,000 meters)?
Ted's grandfather used his treadmill on 3 days this week. He went 2 miles each day. On Monday he jogged at a speed of 5 miles per hour. He walked at the rate of 3 miles per hour on Wednesday and at 4 miles per hour on Friday. If Grandfather had always walked at 4 miles per hour, he would have spent less time on the treadmill. How many minutes less?
At the 2013 Winnebago County Fair a vendor is offering a "fair special" on sandals. If you buy one pair of sandals at the regular price of $50, you get a second pair at a 40% discount, and a third pair at half the regular price. Javier took advantage of the "fair special" to buy three pairs of sandals. What percentage of the $150 regular price did he save?
When Clara totaled her scores, she inadvertently reversed the units digit and the tens digit of one score. By which of the following might her incorrect sum have differed from the correct one?
当 Clara 把她的所有的考试分数相加时,她不小心把某个分数的十位数字和个位数字调换了。那么她不正确的总分和正确总分可能相差多少?
2013 AMC8 #14 · Counting, Probability & Statistics · ★★★
Abe holds 1 green and 1 red jelly bean in his hand. Bob holds 1 green, 1 yellow, and 2 red jelly beans in his hand. Each randomly picks a jelly bean to show the other. What is the probability that the colors match?
A number of students from Fibonacci Middle School are taking part in a community service project. The ratio of 8th -graders to 6th -graders is 5:3 , and the the ratio of 8th -graders to 7th -graders is 8:5 . What is the smallest number of students that could be participating in the project?
Isabella uses one-foot cubical blocks to build a rectangular fort that is 12 feet long, 10 feet wide, and 5 feet high. The floor and the four walls are all one foot thick. How many blocks does the fort contain?
2013 AMC8 #19 · Counting, Probability & Statistics · ★★★
Bridget, Cassie, and Hannah are discussing the results of their last math test. Hannah shows Bridget and Cassie her test, but Bridget and Cassie don't show theirs to anyone. Cassie says, 'I didn't get the lowest score in our class,' and Bridget adds, 'I didn't get the highest score.' What is the ranking of the three girls from highest to lowest?
2013 AMC8 #21 · Counting, Probability & Statistics · ★★★
Samantha lives 2 blocks west and 1 block south of the southwest corner of City Park. Her school is 2 blocks east and 2 blocks north of the northeast corner of City Park. On school days she bikes on streets to the southwest corner of City Park, then takes a diagonal path through the park to the northeast corner, and then bikes on streets to school. If her route is as short as possible, how many different routes can she take?
Angle ABC of △ABC is a right angle. The sides of △ABC are the diameters of semicircles as shown. The area of the semicircle on AB equals 8π, and the arc of the semicircle on AC has length 8.5π. What is the radius of the semicircle on BC?
Squares ABCD , EFGH , and GHIJ are equal in area. Points C and D are the midpoints of sides IH and HE , respectively. What is the ratio of the area of the shaded pentagon AJICB to the sum of the areas of the three squares?
正方形 ABCD,EFGH 和 GHIJ 的面积都相等。点 C 和点 D 分别是边 IH 和 HE 的中点。那么阴影部分五边形 AJICB 的面积和三个正方形面积总和的比值是多少?
A ball with diameter 4 inches starts at point A to roll along the track shown. The track is comprised of 3 semicircular arcs whose radii are R_1 = 100 inches, R_2 = 60 inches, and R_3 = 80 inches, respectively. The ball always remains in contact with the track and does not slip. What is the distance the center of the ball travels over the course from A to B?
直径为 4 英寸的球从 A 开始沿着图示轨道滚动。轨道由 3 段半圆弧组成,半径分别为 R1=100 英寸,R2=60 英寸,R3=80 英寸。球全程都和轨道紧密接触,并且不会滑动。那么当球从 A 滚到 B,球心所经过的路程是多少英寸?
Rachelle uses 3 pounds of meat to make 8 hamburgers for her family. How many pounds of meat does she need to make 24 hamburgers for a neighbourhood picnic?
In the country of East Westmore, statisticians estimate there is a baby born every 8 hours and a death every day. To the nearest hundred, how many people are added to the population of East Westmore each year?
在 East Westmore 这个国家,统计学家们估计,每 8 小时就会有 1 个婴儿出生,并且每天都会有一人去世。那么每年 East Westmore 国家的人口数会增加多少?结果精确到百位.
On February 13 The Oshkosh Northwester listed the length of daylight as 10 hours and 24 minutes, the sunrise was 6:57 AM , and the sunset as 8:15 PM . The length of daylight and sunrise were correct, but the sunset was wrong. When did the sun really set?
Peter's family ordered a 12-slice pizza for dinner. Peter ate one slice and shared another slice equally with his brother Paul. What fraction of the pizza did Peter eat?
Peter 的家人晚餐订了一块 12 片的比萨。Peter 吃了一片,然后和他的弟弟 Paul 平分了另一片。那么 Peter 所吃的比萨饼占整块的比例是多少?
In the diagram, all angles are right angles and the lengths of the sides are given in centimeters. Note that the diagram is not drawn to scale. What is the length of X , in centimeters?
如下图所示,所有的角都是直角,并且边长都是以厘米为单位。注意图形没有按比例给出。
那么 X 代表的长度是多少厘米?
A rectangular photograph is placed in a frame that forms a border two inches wide on all sides of the photograph. The photograph measures 8 inches high and 10 inches wide. What is the area of the border, in square inches?
Isabella must take four 100-point tests in her math class. Her goal is to achieve an average grade of 95 on the tests. Her first two test scores were 97 and 91. After seeing her score on the third test, she realized she can still reach her goal. What is the lowest possible score she could have made on the third test?
A shop advertises everything is "half price in today's sale." In addition, a coupon gives a 20% discount on sale prices. Using the coupon, the price today represents what percentage off the original price?
The Fort Worth Zoo has a number of two-legged birds and a number of four-legged mammals. On one visit to the zoo, Margie counted 200 heads and 522 legs. How many of the animals that Margie counted were two-legged birds?
Jamar bought some pencils costing more than a penny each at the school bookstore and paid $1.43 . Sharona bought some of the same pencils and paid $1.87 . How many more pencils did Sharona buy than Jamar?
2012 AMC8 #14 · Counting, Probability & Statistics · ★★★
In the BIG N, a middle school football conference, each team plays every other team exactly once. If a total of 21 conference games were played during the 2012 season, how many teams were members of the BIG N conference?
2012 AMC8 #16 · Counting, Probability & Statistics · ★★★
Each of the digits 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9 is used only once to make two five-digit numbers so that they have the largest possible sum. Which of the following could be one of the numbers?
A square with integer side length is cut into 10 squares, all of which have integer side length and at least 8 of which have area 1. What is the smallest possible value of the length of the side of the original square?
Marla has a large white cube that has an edge of 10 feet. She also has enough green paint to cover 300 square feet. Marla uses all the paint to create a white square centered on each face, surrounded by a green border. What is the area of one of the white squares, in square feet?
2012 AMC8 #22 · Counting, Probability & Statistics · ★★★★
Let R be a set of nine distinct integers. Six of the elements are 2 , 3 , 4 , 6 , 9 , and 14 . What is the number of possible values of the median of R ?
R 是由 9 个不同的整数组成的集合。其中 6 个元素是 2,3,4,6,9 和 14.那么 R 的中位数有多少个可能的值?
A circle of radius 2 is cut into four congruent arcs. The four arcs are joined to form the star figure shown. What is the ratio of the area of the star figure to the area of the original circle?
A square with area 4 is inscribed in a square with area 5, with one vertex of the smaller square on each side of the larger square. A vertex of the smaller square divides a side of the larger square into two segments, one of length a , and the other of length b . What is the value of ab ?
一个面积为 4 的正方形内接在一个面积为 5 的正方形内,小正方形的每个顶点分别落在大正方形的每条边上。小正方形的某个顶点将大正方形的一条边分成了 2 条线段,长度分别是 a 和 b,那么 ab 的值是多少?
Extend the square pattern of 8 black and 17 white square tiles by attaching a border of black tiles around the square. What is the ratio of black tiles to white tiles in the extended pattern?
2011 AMC8 #6 · Counting, Probability & Statistics · ★★
In a town of 351 adults, every adult owns a car, motorcycle, or both. If 331 adults own cars and 45 adults own motorcycles, how many of the car owners do not own a motorcycle?
Each of the following four large congruent squares is subdivided into combinations of congruent triangles or rectangles and is partially bolded. What percent of the total area is partially bolded?
2011 AMC8 #8 · Counting, Probability & Statistics · ★
Bag A has three chips labeled 1, 3, and 5. Bag B has three chips labeled 2, 4, and 6. If one chip is drawn from each bag, how many different values are possible for the sum of the two numbers on the chips?
口袋 A 中有标有 1,3,5 的三个筹码,口袋 B 中有标有 2,4,6 的三个筹码。若从每个口袋中随机抽出一个筹码,那么这 2 个筹码上的数字之和有多少种可能的不同值?
Carmen takes a long bike ride on a hilly highway. The graph indicates the miles traveled during the time of her ride. What is Carmen's average speed for her entire ride in miles per hour?
The taxi fare in Gotham City is $2.40 for the first 21 mile and additional mileage charged at the rate $0.20 for each additional 0.1 mile. You plan to give the driver a $2 tip. How many miles can you ride for $10 ?
2011 AMC8 #11 · Counting, Probability & Statistics · ★★★
The graph shows the number of minutes studied by both Asha (black bar) and Sasha (grey bar) in one week. On the average, how many more minutes per day did Sasha study than Asha?
2011 AMC8 #12 · Counting, Probability & Statistics · ★★★
Angie, Bridget, Carlos, and Diego are seated at random around a square table, one person to a side. What is the probability that Angie and Carlos are seated opposite each other?
Angie,Bridget,Carlos 和 Diego 随机围着一张方桌坐下,一人坐一边。那么 Angie 和 Carlos 面对面坐着的概率是多少?
Two congruent squares, ABCD and PQRS , have side length 15 . They overlap to form the 15 by 25 rectangle AQRD shown. What percent of the area of rectangle AQRD is shaded?
There are 270 students at Colfax Middle School, where the ratio of boys to girls is 5:4 . There are 180 students at Winthrop Middle School, where the ratio of boys to girls is 4:5 . The two schools hold a dance and all students from both schools attend. What fraction of the students at the dance are girls?
Let A be the area of the triangle with sides of length 25, 25 , and 30 . Let B be the area of the triangle with sides of length 25, 25, and 40 . What is the relationship between A and B ?
A 表示边长为 25,25,30 的三角形的面积,B 表示边长为 25,25,40 的三角形的面积,那么 A 和 B 的关系是什么?
Students guess that Norb's age is 24, 28, 30, 32, 36, 38, 41, 44, 47 , and 49 . Norb says, "At least half of you guessed too low, two of you are off by one, and my age is a prime number." How old is Norb?
2011 AMC8 #23 · Counting, Probability & Statistics · ★★★★
How many 4-digit positive integers have four different digits, where the leading digit is not zero, the integer is a multiple of 5, and 5 is the largest digit?
A circle with radius 1 is inscribed in a square and circumscribed about another square as shown. Which fraction is closest to the ratio of the circle's shaded area to the area between the two squares?
At Euclid Middle School, the mathematics teachers are Miss Germain, Mr. Newton, and Mrs. Young. There are 11 students in Mrs. Germain's class, 8 students in Mr. Newton's class, and 9 students in Mrs. Young's class taking the AMC 8 this year. How many mathematics students at Euclid Middle School are taking the contest?
在欧几里得中学,数学老师是 Germain 小姐,Newton 先生和 Young 女士。Germain 小姐班上的 11 位学生,Newton 先生班上的 8 位学生和 Young 女士班上的 9 位学生今年参加 AMC8 竞赛。那么欧几里得中学今年有多少学数学的学生会参加这次竞赛?
The graph shows the price of five gallons of gasoline during the first ten months of the year. By what percent is the highest price more than the lowest price?
Alice needs to replace a light bulb located 10 centimeters below the ceiling in her kitchen. The ceiling is 2.4 meters above the floor. Alice is 1.5 meters tall and can reach 46 centimeters above the top of her head. Standing on a stool, she can just reach the light bulb. What is the height of the stool, in centimeters?
Alice 需要换掉厨房的一个灯泡,灯泡位于天花板下面 10 厘米,天花板离地面 2.4 米。
Alice 有 1.5 米高,并且可以碰到离她头顶 46 厘米高的地方。当她站在凳子上,她恰好可以碰到灯泡。那么凳子的高度是多少厘米?
2010 AMC8 #7 · Counting, Probability & Statistics · ★★★
Using only pennies, nickels, dimes, and quarters, what is the smallest number of coins Freddie would need so he could pay any amount of money less than a dollar?
As Emily is riding her bicycle on a long straight road, she spots Emerson skating in the same direction 1/2 mile in front of her. After she passes him, she can see him in her rear mirror until he is 1/2 mile behind her. Emily rides at a constant rate of 12 miles per hour, and Emerson skates at a constant rate of 8 miles per hour. For how many minutes can Emily see Emerson?
Ryan got 80% of the problems correct on a 25 -problem test, 90% on a 40 -problem test, and 70% on a 10 -problem test. What percent of all the problems did Ryan answer correctly?
Six pepperoni circles will exactly fit across the diameter of a 12 -inch pizza when placed. If a total of 24 circles of pepperoni are placed on this pizza without overlap, what fraction of the pizza is covered by pepperoni?
The top of one tree is 16 feet higher than the top of another tree. The heights of the two trees are in the ratio 3:4 . In feet, how tall is the taller tree?
Of the 500 balls in a large bag, 80% are red and the rest are blue. How many of the red balls must be removed so that 75% of the remaining balls are red?
The lengths of the sides of a triangle in inches are three consecutive integers. The length of the shortest side is 30% of the perimeter. What is the length of the longest side?
A jar contains 5 different colors of gumdrops. 30% are blue, 20% are brown, 15% are red, 10% are yellow, and other 30 gumdrops are green. If half of the blue gumdrops are replaced with brown gumdrops, how many gumdrops will be brown?
The diagram shows an octagon consisting of 10 unit squares. The portion below PQ is a unit square and a triangle with base 5 . If PQ bisects the area of the octagon, what is the ratio QYXQ?
A decorative window is made up of a rectangle with semicircles on either end. The ratio of AD to AB is 3:2 , and AB is 30 inches. What is the ratio of the area of the rectangle to the combined areas of the semicircles?
The two circles pictured have the same center C . Chord AD is tangent to the inner circle at B , AC is 10 , and chord AD has length 16 . What is the area between the two circles?
下图中的两个圆是同心圆,圆心都是 C。弦 AD 与内圆切于 B,AC 长为 10,弦 AD 长为 16。那么这两个圆之间区域的面积是多少?
2010 AMC8 #20 · Counting, Probability & Statistics · ★★★
In a room, 2/5 of the people are wearing gloves, and 3/4 of the people are wearing hats. What is the minimum number of people in the room wearing both a hat and gloves?
Hui is an avid reader. She bought a copy of the best seller Math is Beautiful. On the first day, Hui read 1/5 of the pages plus 12 more, and on the second day she read 1/4 of the remaining pages plus 15 pages. On the third day she read 1/3 of the remaining pages plus 18 pages. She then realized that there were only 62 pages left to read, which she read the next day. How many pages are in this book?
The hundreds digit of a three-digit number is 2 more than the units digit. The digits of the three-digit number are reversed, and the result is subtracted from the original three-digit number. What is the units digit of the result?
2010 AMC8 #25 · Counting, Probability & Statistics · ★★★★
Everyday at school, Jo climbs a flight of 6 stairs. Jo can take the stairs 1 , 2 , or 3 at a time. For example, Jo could climb 3 , then 1 , then 2 . In how many ways can Jo climb the stairs?
Jo 每天在学校里都要爬 6 节楼梯。Jo 可以一次爬 1 节,2 节或者 3 节。例如,J0 可以先一次爬 3 节,然后 1 节,然后 2 节。则 Jo 爬楼梯一共有多少种可能的方法?
Bridget bought a bag of apples at the grocery store. She gave half of the apples to Ann. Then she gave Cassie 3 apples, keeping 4 apples for herself. How many apples did Bridget buy?
On average, for every 4 sports cars sold at the local dealership, 7 sedans are sold. The dealership predicts that it will sell 28 sports cars next month. How many sedans does it expect to sell?
The graph shows the constant rate at which Suzanna rides her bike. If she rides a total of a half an hour at the same speed, how many miles would she have ridden?
A sequence of numbers starts with 1 , 2 , and 3 . The fourth number of the sequence is the sum of the previous three numbers in the sequence: 1+2+3=6 . In the same way, every number after the fourth is the sum of the previous three numbers. What is the eighth number in the sequence?
Steve's empty swimming pool will hold 24,000 gallons of water when full. It will be filled by 4 hoses, each of which supplies 2.5 gallons of water per minute. How many hours will it take to fill Steve's pool?
Steve 家的游泳池当装满水时,能装 24,000 加仑的水。现在将由 4 个水管同时灌水,每个水管每分钟灌水 2.5 加仑。那么将 Steve 家的泳池灌满水要多少小时?
The triangular plot of ACD lies between Aspen Road, Brown Road and a railroad. Main Street runs east and west, and the railroad runs north and south. The numbers in the diagram indicate distances in miles. The width of the railroad track can be ignored. How many square miles are in the plot of land ACD?
Construct a square on one side of an equilateral triangle. On one non-adjacent side of the square, construct a regular pentagon, as shown. On a non-adjacent side of the pentagon, construct a hexagon. Continue to construct regular polygons in the same way, until you construct an octagon. How many sides does the resulting polygon have?
The Amaco Middle School bookstore sells pencils costing a whole number of cents. Some seventh graders each bought a pencil, paying a total of $1.43. Some of the 30 sixth graders each bought a pencil, and they paid a total of $1.95. How many more sixth graders than seventh graders bought a pencil?
2009 AMC8 #12 · Counting, Probability & Statistics · ★★★
The two spinners shown are spun once and each lands on one of the numbered sectors. What is the probability that the sum of the numbers in the two sectors is prime?
Austin and Temple are 50 miles apart along Interstate 35. Bonnie drove from Austin to her daughter's house in Temple, averaging 60 miles per hour. Leaving the car with her daughter, Bonnie rode a bus back to Austin along the same route and averaged 40 miles per hour on the return trip. What was the average speed for the round trip, in miles per hour?
A recipe that makes 5 servings of hot chocolate requires 2 squares of chocolate, 41 cup sugar, 1 cup water and 4 cups milk. Jordan has $5$ squares of chocolate, 2 cups of sugar, lots of water, and 7 cups of milk. If he maintains the same ratio of ingredients, what is the greatest number of servings of hot chocolate he can make?
The positive integers x and y are the two smallest positive integers for which the product of 360 and x is a square and the product of 360 and y is a cube. What is the sum of x and y ?
x 和 y 是满足 360 和 x 之积为平方数,360 和 y 之积为立方数的最小正整数。那么 x 和 y 的和是多少?
The diagram represents a 7-foot-by-7-foot floor that is tiled with 1-square-foot black tiles and white tiles. Notice that the corners have white tiles. If a 15-foot-by-15-foot floor is to be tiled in the same manner, how many white tiles will be needed?
Andy and Bethany have a rectangular array of numbers greater than 0 with 40 rows and 75 columns. Andy adds the numbers in each row. The average of his 40 sums is A . Bethany adds the numbers in each column. The average of her 75 sums is B . What is the value of BA ?
On the last day of school, Mrs. Wonderful gave jelly beans to her class. She gave each boy as many jelly beans as there were boys in the class. She gave each girl as many jelly beans as there were girls in the class. She brought 400 jelly beans, and when she finished, she had six jelly beans left. There were two more boys than girls in her class. How many students were in her class?
A one-cubic-foot cube is cut into four pieces by three cuts parallel to the top face of the cube. The first cut is 1/2 foot from the top face. The second cut is 1/3 foot below the first cut, and the third cut is 1/17 foot below the second cut. From the top to the bottom the pieces are labeled A, B, C, and D. The pieces are then glued together end to end as shown in the second diagram. What is the total surface area of this solid in square feet?
In the figure, the outer equilateral triangle has area 16 , the inner equilateral triangle has area 1 , and the three trapezoids are congruent. What is the area of one of the trapezoids?
Barney Schwinn notices that the odometer on his bicycle reads 1441 , a palindrome, because it reads the same forward and backward. After riding 4 more hours that day and 6 the next, he notices that the odometer shows another palindrome, 1661 . What was his average speed in miles per hour?
In 2005 Tycoon Tammy invested 100 dollars for two years. During the first year her investment suffered a 15% loss, but during the second year the remaining investment showed a 20% gain. Over the two-year period, what was the change in Tammy's investment?
2008 AMC8 #10 · Counting, Probability & Statistics · ★★
The average age of the 6 people in Room A is 40 . The average age of the 4 people in Room B is 25 . If the two groups are combined, what is the average age of all the people?
2008 AMC8 #11 · Counting, Probability & Statistics · ★★★
Each of the 39 students in the eighth grade at Lincoln Middle School has one dog or one cat or both a dog and a cat. Twenty students have a dog and 26 students have a cat. How many students have both a dog and a cat?
A ball is dropped from a height of 3 meters. On its first bounce it rises to a height of 2 meters. It keeps falling and bouncing to 32 of the height it reached in the previous bounce. On which bounce will it rise to a height less than 0.5 meters?
Mr. Harman needs to know the combined weight in pounds of three boxes he wants to mail. However, the only available scale is not accurate for weights less than 100 pounds or more than 150 pounds. So the boxes are weighed in pairs in every possible way. The results are 122 , 125 and 127 pounds. What is the combined weight in pounds of the three boxes?
2008 AMC8 #14 · Counting, Probability & Statistics · ★★★
Three A’s, three B’s, and three C’s are placed in the nine spaces so that each row and column contain one of each letter. If A is placed in the upper left corner, how many arrangements are possible?
把三个 A,三个 B 和三个 C 放置在九个空格中,使得每行和每列包含三个字母中的每一个字母。
如果 A 放置在左上角,那么一共有多少种安排方法?
In Theresa's first 8 basketball games, she scored 7, 4, 3, 6, 8, 3, 1 and 5 points. In her ninth game, she scored fewer than 10 points and her points-per-game average for the nine games was an integer. Similarly in her tenth game, she scored fewer than 10 points and her points-per-game average for the 10 games was also an integer. What is the product of the number of points she scored in the ninth and tenth games?
Ms.Osborne asks each student in her class to draw a rectangle with integer side lengths and a perimeter of 50 units. All of her students calculate the area of the rectangle they draw. What is the difference between the largest and smallest possible areas of the rectangles?
Two circles that share the same center have radii 10 meters and 20 meters. An aardvark runs along the path shown, starting at A and ending at K . How many meters does the aardvark run?
两个同心圆的半径分别是 10 米和 20 米。一个土豚沿着图示路径运动,从 A 点开始到 K 点结束。则土豚总共运动了多少米?
2008 AMC8 #19 · Counting, Probability & Statistics · ★★★
Eight points are spaced around at intervals of one unit around a 2×2 square, as shown. Two of the 8 points are chosen at random. What is the probability that the two points are one unit apart?
The students in Mr. Neatkin's class took a penmanship test. Two-thirds of the boys and 43 of the girls passed the test, and an equal number of boys and girls passed the test. What is the minimum possible number of students in the class?
Jerry cuts a wedge from a 6 -cm cylinder of bologna as shown by the dashed curve. Which answer choice is closest to the volume of his wedge in cubic centimeters?
2008 AMC8 #24 · Counting, Probability & Statistics · ★★★★
Ten tiles numbered 1 through 10 are turned face down. One tile is turned up at random, and a die is rolled. What is the probability that the product of the numbers on the tile and the die will be a square?
Margie's winning art design is shown. The smallest circle has radius 2 inches, with each successive circle's radius increasing by 2 inches. Which of the following is closest to the percent of the design that is black?
2007 AMC8 #1 · Counting, Probability & Statistics · ★
Theresa's parents have agreed to buy her tickets to see her favorite band if she spends an average of 10 hours per week helping around the house for 6 weeks. For the first 5 weeks she helps around the house for 8 , 11 , 7 , 12 and 10 hours. How many hours must she work for the final week to earn the tickets?
2007 AMC8 #2 · Counting, Probability & Statistics · ★
650 students were surveyed about their pasta preferences. The choices were lasagna, manicotti, ravioli and spaghetti. The results of the survey are displayed in the bar graph. What is the ratio of the number of students who preferred spaghetti to the number of students who preferred manicotti?
Chandler wants to buy a 500 dollar mountain bike. For his birthday, his grandparents send him 50 dollars, his aunt sends him 35 dollars and his cousin gives him 15 dollars. He earns $16$ dollars per week for his paper route. He will use all of his birthday money and all of the money he earns from his paper route. In how many weeks will he be able to buy the mountain bike?
The average cost of a long-distance call in the USA in 1985 was 41 cents per minute, and the average cost of a long-distance call in the USA in 2005 was 7 cents per minute. Find the approximate percent decrease in the cost per minute of a long- distance call.
2007 AMC8 #9 · Counting, Probability & Statistics · ★★
To complete the grid below, each of the digits 1 through 4 must occur once in each row and once in each column. What number will occupy the lower right-hand square?
2007 AMC8 #11 · Counting, Probability & Statistics · ★★★
Tiles $I, II, III$ and IV are translated so one tile coincides with each of the rectangles A, B, C and D . In the final arrangement, the two numbers on any side common to two adjacent tiles must be the same. Which of the tiles is translated to Rectangle C ?
瓷砖 I,II,III 和 IV 被平移至与长方形 A,B,C,D 重合。排列完毕后,要求两块相邻的瓷砖的公共边上的数必须相等。那么哪块瓷砖平移到了长方形 C 上?
A unit hexagram is composed of a regular hexagon of side length 1 and its 6 equilateral triangular extensions, as shown in the diagram. What is the ratio of the area of the extensions to the area of the original hexagon?
2007 AMC8 #13 · Counting, Probability & Statistics · ★★★
Sets A and B, shown in the Venn diagram, have the same number of elements. Their union has 2007 elements and their intersection has 1001 elements. Find the number of elements in A.
如下图所示的文氏图中,集合 A 和集合 B 中的元素个数相等。它们的并集有 2007 个元素,且它们的交集有 1001 个元素。那么求集合 A 中的元素个数。
Amanda draws five circles with radii 1, 2, 3, 4 and 5. Then for each circle she plots the point (C,A), where C is its circumference and A is its area. Which of the following could be her graph?
A mixture of 30 liters of paint is 25% red tint, 30% yellow tint and 45% water. Five liters of yellow tint are added to the original mixture. What is the percent of yellow tint in the new mixture?
The product of the two 99 -digit numbers 303,030,303,...,030,303 and 505,050,505,...,050,505 has thousands digit A and units digit B . What is the sum of A and B ?
两个 99 位数字 303,030,303,…,030,303 和 505,050,505,…,050,505 的乘积的千位数字为 A,个位数字是 B。那么 A 与 B 的和是多少?
Pick two consecutive positive integers whose sum is less than 100 . Square both of those integers and then find the difference of the squares. Which of the following could be the difference?
Before the district play, the Unicorns had won 45% of their basketball games. During district play, they won six more games and lost two, to finish the season having won half their games. How many games did the Unicorns play in all?
2007 AMC8 #21 · Counting, Probability & Statistics · ★★★
Two cards are dealt from a deck of four red cards labeled A , B , C , D and four green cards labeled A , B , C , D . A winning pair is two of the same color or two of the same letter. What is the probability of drawing a winning pair?
A lemming sits at a corner of a square with side length 10 meters. The lemming runs 6.2 meters along a diagonal toward the opposite corner. It stops, makes a 90∘ right turn and runs 2 more meters. A scientist measures the shortest distance between the lemming and each side of the square. What is the average of these four distances in meters?
2007 AMC8 #24 · Counting, Probability & Statistics · ★★★★
A bag contains four pieces of paper, each labeled with one of the digits 1 , 2 , 3 or 4 , with no repeats. Three of these pieces are drawn, one at a time without replacement, to construct a three-digit number. What is the probability that the three-digit number is a multiple of 3 ?
2007 AMC8 #25 · Counting, Probability & Statistics · ★★★★
On the dart board shown in the figure, the outer circle has radius 6 and the inner circle has a radius of 3. Three radii divide each circle into three congruent regions, with point values shown. The probability that a dart will hit a given region is proportional to the area of the region. When two darts hit this board, the score is the sum of the point values in the regions. What is the probability that the score is odd?
Elisa swims laps in the pool. When she first started, she completed 10 laps in 25 minutes. Now she can finish 12 laps in 24 minutes. By how many minutes has she improved her lap time?
Initially, a spinner points west. Chenille moves it clockwise 241 revolutions and then counterclockwise 343 revolutions. In what direction does the spinner point after the two moves?
Jorge's teacher asks him to plot all the ordered pairs (w, l) of positive integers for which w is the width and l is the length of a rectangle with area 12. What should his graph look like?
Jorget 的老师要求他画出所有的(w,l)正整数对,其中 w 和 l 分别是一个面积为 12 的矩形的宽和长。则他画的图应该是下面哪个?
Antonette gets 70 % on a 10-problem test, 80 % on a 20-problem test and 90 % on a 30-problem test. If the three tests are combined into one 60-problem test, which percent is closest to her overall score?
Cassie leaves Escanaba at 8:30 AM heading for Marquette on her bike. She bikes at a uniform rate of 12 miles per hour. Brian leaves Marquette at 9:00 AM heading for Escanaba on his bike. He bikes at a uniform rate of 16 miles per hour. They both bike on the same 62-mile route between Escanaba and Marquette. At what time in the morning do they meet?
Problems 14, 15 and 16 involve Mrs. Reed's English assignment. A Novel Assignment The students in Mrs. Reed's English class are reading the same 760 -page novel. Three friends, Alice, Bob and Chandra, are in the class. Alice reads a page in 20 seconds, Bob reads a page in 45 seconds and Chandra reads a page in 30 seconds. If Bob and Chandra both read the whole book, Bob will spend how many more seconds reading than Chandra?
Problems 14, 15 and 16 involve Mrs. Reed's English assignment. A Novel Assignment The students in Mrs. Reed's English class are reading the same 760-page novel. Three friends, Alice, Bob and Chandra, are in the class. Alice reads a page in 20 seconds, Bob reads a page in 45 seconds and Chandra reads a page in 30 seconds. Chandra and Bob, who each have a copy of the book, decide that they can save time by "team reading" the novel. In this scheme, Chandra will read from page 1 to a certain page and Bob will read from the next page through page 760, finishing the book. When they are through they will tell each other about the part they read. What is the last page that Chandra should read so that she and Bob spend the same amount of time reading the novel?
Chandra 和 Bob 各自都有这本书,他们决定通过”团队阅读”这本小说来节省时间。在这种方案下,Chandra 会从第一页读到某一页,Bob 会从下一页一直读到第 760 页,把书读完。当他们都完成各自的任务,他们会告诉对方自己所读的内容。那么为了使得 Chandra 和 Bob 阅读的时间相同,Chandra 所读的最后一页是第几页?
Problems 14, 15 and 16 involve Mrs. Reed's English assignment. A Novel Assignment The students in Mrs. Reed's English class are reading the same 760-page novel. Three friends, Alice, Bob and Chandra, are in the class. Alice reads a page in 20 seconds, Bob reads a page in 45 seconds and Chandra reads a page in 30 seconds. Before Chandra and Bob start reading, Alice says she would like to team read with them. If they divide the book into three sections so that each reads for the same length of time, how many seconds will each have to read?
在 Chandra 和 Bob 开始阅读前,Alice 说她想加入和他俩一起团队阅读。若他们把书分成 3 部分,使得每人阅读时间都相同,那么每人阅读时间是多少秒?
A cube with 3-inch edges is made using 27 cubes with 1-inch edges. Nineteen of the smaller cubes are white and eight are black. If the eight black cubes are placed at the corners of the larger cube, what fraction of the surface area of the larger cube is white?
Triangle ABC is an isosceles triangle with AB=BC. Point D is the midpoint of both BC and AE, and CE is 11 units long. Triangle ABD is congruent to triangle ECD . What is the length of BD?
三角形 ABC 是个等腰三角形,。点 D 是线段的中点,同时也是线段的中点。
线段长度为 11 个单位。三角形 ABD 和三角形 ECD 全等的,则的长度是多少?
2006 AMC8 #20 · Counting, Probability & Statistics · ★★★
A singles tournament had six players. Each player played every other player only once, with no ties. If Helen won 4 games, Ines won 3 games, Janet won 2 games, Kendra won 2 games and Lara won 2 games, how many games did Monica win?
An aquarium has a rectangular base that measures 100 cm by 40 cm and has a height of 50 cm. The aquarium is filled with water to a depth of 37 cm. A rock with volume 1000cm3 is then placed in the aquarium and completely submerged. By how many centimeters does the water level rise?
Three different one-digit positive integers are placed in the bottom row of cells. Numbers in adjacent cells are added and the sum is placed in the cell above them. In the second row, continue the same process to obtain a number in the top cell. What is the difference between the largest and smallest numbers possible in the top cell?
A box contains gold coins. If the coins are equally divided among six people, four coins are left over. If the coins are equally divided among five people, three coins are left over. If the box holds the smallest number of coins that meets these two conditions, how many coins are left when equally divided among seven people?
Barry wrote 6 different numbers, one on each side of 3 cards, and laid the cards on a table, as shown. The sums of the two numbers on each of the three cards are equal. The three numbers on the hidden sides are prime numbers. What is the average of the hidden prime numbers?
Connie multiplies a number by 2 and gets 60 as her answer. However, she should have divided the number by 2 to get the correct answer. What is the correct answer?
Karl bought five folders from Pay-A-Lot at a cost of $2.50 each. Pay-A-Lot had a 20%-off sale the following day. How much could Karl have saved on the purchase by waiting a day?
Karl 从 Pay-A-Lot 买了五个文件夹,每个价格为 2.5 美元。Pay-A-Lot 第二天降价 20%。那么 Karl 如果等一天他本可以省下多少钱?
A square and a triangle have equal perimeters. The lengths of the three sides of the triangle are 6.1 cm, 8.2 cm and 9.7 cm. What is the area of the square in square centimeters?
In quadrilateral ABCD , sides AB and BC both have length 10, sides CD and DA both have length 17, and the measure of angle ADC is 60∘. What is the length of diagonal AC?
四边形 ABCD 中,边 AB 和 BC 的长度都是 10,边 CD 和 DA 的长度都是 17,且 ∠ADC=60∘。那么对角线 AC 的长度是多少?
Joe had walked half way from home to school when he realized he was late. He ran the rest of the way to school. He ran 3 times as fast as he walked. Joe took 6 minutes to walk half way to school. How many minutes did it take Joe to get from home to school?
Joe 从家步行去学校,当他意识到自己已经迟到时,已经走了总路程的一半,他跑完了剩下的路程,跑步的速度是步行速度的 3 倍。已知 Joe 步行的一半路程耗时 6 分钟,那么他从家到学校总共花了多少分钟?
The sales tax rate in Rubenenkoville is 6%. During a sale at the Bergville Coat Closet, the price of a coat is discounted 20% from its $90.00 price. Two clerks, Jack and Jill, calculate the bill independently. Jack rings up $90.00 and adds 6% sales tax, then subtracts 20% from this total. Jill rings up $90.00, subtracts 20% of the price, then adds 6% of the discounted price for sales tax. What is Jack's total minus Jill's total?
Big Al, the ape, ate 100 bananas from May 1 through May 5. Each day he ate six more bananas than on the previous day. How many bananas did Big Al eat on May 5?
2005 AMC8 #14 · Counting, Probability & Statistics · ★★★
The Little Twelve Basketball Conference has two divisions, with six teams in each division. Each team plays each of the other teams in its own division twice and every team in the other division once. How many conference games are scheduled?
2005 AMC8 #16 · Counting, Probability & Statistics · ★★★
A five-legged Martian has a drawer full of socks, each of which is red, white or blue, and there are at least five socks of each color. The Martian pulls out one sock at a time without looking. How many socks must the Martian remove from the drawer to be certain there will be 5 socks of the same color?
Alice and Bob play a game involving a circle whose circumference is divided by 12 equally-spaced points. The points are numbered clockwise, from 1 to 12. Both start on point 12. Alice moves clockwise and Bob, counterclockwise. In a turn of the game, Alice moves 5 points clockwise and Bob moves 9 points counterclockwise. The game ends when they stop on the same point. How many turns will this take?
Alice 和 Bob 玩了一个游戏,游戏中有一个圆的周长被 12 个等距点分成 12 等份。这些点按顺时针方向从 1 到 12 编号。两个人都从第 12 个点开始。Alice 顺时针移动,而 Bob 逆时针移动。
在游戏的每个回合,Alice 顺时针移动 5 个点,Bob 逆时针移动 9 个点。当他们停在同一点上时,比赛结束。则到游戏结束一共需要经过多少个回合?
A company sells detergent in three different sized boxes: small (S), medium (M) and large (L). The medium size costs 50% more than the small size and contains 20% less detergent than the large size. The large size contains twice as much detergent as the small size and costs 30% more than the medium size. Rank the three sizes from best to worst buy.
Isosceles right triangle ABC encloses a semicircle of area 2π. The circle has its center O on hypotenuse AB and is tangent to sides AC and BC. What is the area of triangle ABC ?
等腰直角三角形 ABC 内含一个面积为 2π 的半圆。该半圆圆心 O 在斜边 AB 上,且与边 AC 和 BC 相切。那么三角形 ABC 的面积是多少?
2005 AMC8 #24 · Counting, Probability & Statistics · ★★★★
A certain calculator has only two keys [+1] and [x2]. When you press one of the keys, the calculator automatically displays the result. For instance, if the calculator originally displayed "9" and you pressed [+1], it would display "10." If you then pressed [x2], it would display "20." Starting with the display "1," what is the fewest number of keystrokes you would need to reach "200"?
A square with side length 2.0 and a circle share the same center. The total area of the regions that are inside the circle and outside the square is equal to the total area of the regions that are outside the circle and inside the square. What is the radius of the circle?
Twelve friends met for dinner at Oscar's Overstuffed Oyster House, and each ordered one meal. The portions were so large, there was enough food for 18 people. If they shared, how many meals should they have ordered to have just enough food for the 12 of them?
2004 AMC8 #5 · Counting, Probability & Statistics · ★★
Ms. Hamilton's eighth-grade class wants to participate in the annual three-person-team basketball tournament. The losing team of each game is eliminated from the tournament. If sixteen teams compete, how many games will be played to determine the winner?
Hamilton 女士八年级的班级想参加一年一度的三人篮球团体赛。每场比赛的败队被淘汰出局。如果有 16 支球队参加比赛,将进行多少场比赛来决定最终的冠军?
After Sally takes 20 shots, she has made 55% of her shots. After she takes 5 more shots, she raises her percentage to 56% . How many of the last 5 shots did she make?
An athlete's target heart rate, in beats per minute, is 80% of the theoretical maximum heart rate. The maximum heart rate is found by subtracting the athlete's age, in years, from 220 . To the nearest whole number, what is the target heart rate of an athlete who is 26 years old?
Handy Aaron helped a neighbor 141 hours on Monday, 50 minutes on Tuesday, from 8:20 to 10:45 on Wednesday morning, and a half-hour on Friday. He is paid $3 per hour. How much did he earn for the week?
2004 AMC8 #11 · Counting, Probability & Statistics · ★★★
The numbers -2, 4, 6, 9 and 12 are rearranged according to these rules:
1. The largest isn't first, but it is in one of the first three places.
2. The smallest isn't last, but it is in one of the last three places.
3. The median isn't first or last.
What is the average of the first and last numbers?
Niki usually leaves her cell phone on. If her cell phone is on but she is not actually using it, the battery will last for 24 hours. If she is using it constantly, the battery will last for only 3 hours. Since the last recharge, her phone has been on 9 hours, and during that time she has used it for 60 minutes. If she doesn’t use it any more but leaves the phone on, how many more hours will the battery last?
Thirteen black and six white hexagonal tiles were used to create the figure below. If a new figure is created by attaching a border of white tiles with the same size and shape as the others, what will be the difference between the total number of white tiles and the total number of black tiles in the new figure?
Two 600 mL pitchers contain orange juice. One pitcher is 1/3 full and the other pitcher is 2/5 full. Water is added to fill each pitcher completely, then both pitchers are poured into one large container. What fraction of the mixture in the large container is orange juice?
两个容量为 600 mL 的罐子里装有橙汁。一个罐子装了 31,另一个装了 52。向每个罐子加水使其装满,然后把两个罐子的液体都倒入一个大容器中。那么大容器里的混合液中橙汁占的比例是多少?
2004 AMC8 #18 · Counting, Probability & Statistics · ★★★
Five friends compete in a dart-throwing contest. Each one has two darts to throw at the same circular target, and each individual's score is the sum of the scores in the target regions that are hit. The scores for the target regions are the whole numbers 1 through 10 . Each throw hits the target in a region with a different value. The scores are: Alice 16 points, Ben 4 points, Cindy 7 points, Dave 11 points, and Ellen 17 points. Who hits the region worth 6 points?
A whole number larger than 2 leaves a remainder of 2 when divided by each of the numbers 3, 4, 5, and 6 . The smallest such number lies between which two numbers?
Two-thirds of the people in a room are seated in three-fourths of the chairs. The rest of the people are standing. If there are 6 empty chairs, how many people are in the room?
2004 AMC8 #21 · Counting, Probability & Statistics · ★★★
Spinners A and B are spun. On each spinner, the arrow is equally likely to land on each number. What is the probability that the product of the two spinners' numbers is even?
将转盘 A 和 B 各旋转一次。已知在每个转盘上,指针落在每个数字上的可能性都相同,那么这两个转盘上(指针所指的)数字之积为偶数的概率是多少?
At a party there are only single women and married men with their wives. The probability that a randomly selected woman is single is 52 . What fraction of the people in the room are married men?
In the figure, ABCD is a rectangle and EFGH is a parallelogram. Using the measurements given in the figure, what is the length d of the segment that is perpendicular to HE and FG ?
如下图所示,ABCD 是个矩形,EFGH 是个平行四边形。使用图中所标线段的长度,则同时垂直于和的线段长度 d 是多少?
Two 4×4 squares intersect at right angles, bisecting their intersecting sides, as shown. The circle's diameter is the segment between the two points of intersection. What is the area of the shaded region created by removing the circle from the squares?
Jamie counted the number of edges of a cube, Jimmy counted the numbers of corners, and Judy counted the number of faces. They then added the three numbers. What was the resulting sum?
A group of children riding on bicycles and tricycles rode past Billy Bob's house. Billy Bob counted 7 children and 19 wheels. How many tricycles were there?
一群骑自行车和三轮车的孩子经过 Billy Bob 的家。Billy Bob 数了数,一共数到了 7 个孩子和 19 个轮子,那么有多少辆三轮车?
Blake and Jenny each took four 100 -point tests. Blake averaged 78 on the four tests. Jenny scored 10 points higher than Blake on the first test, 10 points lower than him on the second test, and 20 points higher on both the third and fourth tests. What is the difference between Jenny's average and Blake's average on these four tests?
Problems 8, 9 and 10 use the data found in the accompanying paragraph and figures
Four friends, Art, Roger, Paul and Trisha, bake cookies, and all cookies have the same thickness. The shapes of the cookies differ, as shown.
∘ Art's cookies are trapezoids:
∘ Roger's cookies are rectangles:
∘ Paul's cookies are parallelograms:
∘ Trisha's cookies are triangles:
Each friend uses the same amount of dough, and Art makes exactly 12 cookies. Art's cookies sell for 60 cents each. To earn the same amount from a single batch, how much should one of Roger's cookies cost in cents?
每个朋友都用了等量的面团,Art 正好做了 12 块饼干。Art 的饼干每个卖 60 美分。为了从这批面团赚得同样的钱,那么 Roger 的饼干应该每个卖多少美分?
Business is a little slow at Lou's Fine Shoes, so Lou decides to have a sale. On Friday, Lou increases all of Thursday's prices by 10 percent. Over the weekend, Lou advertises the sale: "Ten percent off the listed price. Sale starts Monday." How much does a pair of shoes cost on Monday that cost 40 dollars on Thursday?
2003 AMC8 #12 · Counting, Probability & Statistics · ★★★
When a fair six-sided dice is tossed on a table top, the bottom face cannot be seen. What is the probability that the product of the faces that can be seen is divisible by 6 ?
Fourteen white cubes are put together to form the figure on the right. The complete surface of the figure, including the bottom, is painted red. The figure is then separated into individual cubes. How many of the individual cubes have exactly four red faces
A figure is constructed from unit cubes. Each cube shares at least one face with another cube. What is the minimum number of cubes needed to build a figure with the front and side views shown?
2003 AMC8 #16 · Counting, Probability & Statistics · ★★★
Ali, Bonnie, Carlo, and Dianna are going to drive together to a nearby theme park. The car they are using has $4$ seats: 1 Driver seat, 1 front passenger seat, and 2 back passenger seats. Bonnie and Carlo are the only ones who know how to drive the car. How many possible seating arrangements are there?
2003 AMC8 #17 · Counting, Probability & Statistics · ★★★
The six children listed in the table below are from two families of three siblings each. Each child has blue or brown eyes and black or blond hair. Children from the same family have at least one of these characteristics in common. Which two children are Jim's siblings?
下面列出的六名儿童来自两个家庭,每个家庭有三个兄弟姐妹。每个孩子都有蓝色或棕色的眼睛,和黑色或金色的头发。来自同一家庭的儿童至少有一个共同特征。哪两个孩子是 Jim 的兄弟姐妹?
2003 AMC8 #18 · Counting, Probability & Statistics · ★★★
Each of the twenty dots on the graph below represents one of Sarah's classmates. Classmates who are friends are connected with a line segment. For her birthday party, Sarah is inviting only the following: all of her friends and all of those classmates who are friends with at least one of her friends. How many classmates will not be invited to Sarah's party?
下图中的 20 个点中的每个点代表 Sarah 的一个同班同学。这些同班同学中,若某两人之间是朋友关系,则用线段将这两人相连。Sarah 只打算邀请符合下面条件的人参加她的生日聚会:
她的所有朋友,以及所有与她的至少一个朋友是朋友。有多少同学不会被邀请参加 Sarah 的聚会?
In the pattern below, the cat moves clockwise through the four squares, and the mouse moves counterclockwise through the eight exterior segments of the four squares.
If the pattern is continued, where would the cat and mouse be after the 247th move?
A ship travels from point A to point B along a semicircular path, centered at Island X . Then it travels along a straight path from B to C . Which of these graphs best shows the ship's distance from Island X as it moves along its course?
一艘船沿着以岛 X 为圆心的半圆形路径从点 A 航行到点 B。然后它沿着直线路径从 B 到 C。下面这些图表中哪一个最能显示当船沿航线行驶时,船与岛 X 的距离变化?
In the figure, the area of square WXYZ is 25 cm2 . The four smaller squares have sides 1 cm long, either parallel to or coinciding with the sides of the large square. In △ABC , AB = AC , and when △ABC is folded over side BC , point A coincides with O , the center of square WXYZ . What is the area of △ABC , in square centimeters?
在下图中,正方形 WXYZ 的面积为 25 平方厘米。四个小正方形边长为 1 厘米,它们的各边与大正方形的边平行或重合。在中,,若将沿着边折叠,则点 A 和正方形的中心 重合。那么的面积是多少平方厘米?
The year 2002 is a palindrome (a number that reads the same from left to right as it does from right to left). What is the product of the digits of the next year after 2002 that is a palindrome?
A birdbath is designed to overflow so that it will be self-cleaning. Water flows in at the rate of 20 milliliters per minute and drains at the rate of 18 milliliters per minute. Which one of these graphs shows the volume of water in the birdbath during the filling time and continuing into the overflow time?
2002 AMC8 #7 · Counting, Probability & Statistics · ★
The students in Mrs. Sawyer's class were asked to do a taste test of five kinds of candy. Each student chose one kind of candy. A bar graph of their preferences is shown. What percent of her class chose candy E?
2002 AMC8 #8 · Counting, Probability & Statistics · ★★
Problems 8,9 and 10 use the data found in the accompanying paragraph and table:
Juan organizes the stamps in his collection by country and by the decade in which they were issued. The prices he paid for them at a stamp shop were: Brazil and France, 6 cents each, Peru 4 cents each, and Spain 5 cents each. (Brazil and Peru are South American countries and France and Spain are in Europe.)
How many of his European stamps were issued in the '80s?
2002 AMC8 #9 · Counting, Probability & Statistics · ★★
Problems 8,9 and 10 use the data found in the accompanying paragraph and table:
Juan organizes the stamps in his collection by country and by the decade in which they were issued. The prices he paid for them at a stamp shop were: Brazil and France, 6 cents each, Peru 4 cents each, and Spain 5 cents each. (Brazil and Peru are South American countries and France and Spain are in Europe.)
In dollars and cents, how much did his South American stamps issued before the ’70s cost him?
2002 AMC8 #10 · Counting, Probability & Statistics · ★★
Problems 8,9 and 10 use the data found in the accompanying paragraph and table:
Juan organizes the stamps in his collection by country and by the decade in which they were issued. The prices he paid for them at a stamp shop were: Brazil and France, 6 cents each, Peru 4 cents each, and Spain 5 cents each. (Brazil and Peru are South American countries and France and Spain are in Europe.)
The average price of his '70s stamps is closest to
A sequence of squares is made of identical square tiles. The edge of each square is one tile length longer than the edge of the previous square. The first three squares are shown. How many more tiles does the seventh square require than the sixth?
2002 AMC8 #12 · Counting, Probability & Statistics · ★★
A board game spinner is divided into three regions labeled A , B and C . The probability of the arrow stopping on region A is 31 and on region B is 21 . The probability of the arrow stopping on region C is:
一种棋盘游戏的转盘分成 A、B、C 三个区域。已知箭头停在区域 A 的概率为 31,停在区域 B 的概率为 21。那么箭头停在区域 C 的概率是:
For his birthday, Bert gets a box that holds 125 jellybeans when filled to capacity. A few weeks later, Carrie gets a larger box full of jellybeans. Her box is twice as high, twice as wide and twice as long as Bert's. Approximately, how many jellybeans did Carrie get?
Right isosceles triangles are constructed on the sides of a right triangle, as shown. A capital letter represents the area of each triangle. Which one of the following is true?
In a mathematics contest with ten problems, a student gains 5 points for a correct answer and loses 2 points for an incorrect answer. If Olivia answered every problem and her score was 29, how many correct answers did she have?
Gage skated 1 hr 15 min each day for 5 days and 1 hr 30 min each day for 3 days. How long would he have to skate the ninth day in order to average 85 minutes of skating each day for the entire time?
The area of triangle XYZ is 8 square inches. Points A and B are midpoints of congruent segments XY and XZ . Altitude XC bisects YZ . The area (in square inches) of the shaded region is
三角形 XYZ 的面积是 8 平方英寸。点 A 和点 B 分别是两条相等线段 XY 和 XZ 的中点,高 XC 平分 YZ。那么阴影部分的面积是多少平方英寸?
A corner of a tiled floor is shown. If the entire floor is tiled in this way and each of the four corners looks like this one, then what fraction of the tiled floor is made of darker tiles?
Miki has a dozen oranges of the same size and a dozen pears of the same size. Miki uses her juicer to extract 8 ounces of pear juice from 3 pears and 8 ounces of orange juice from 2 oranges. She makes a pear-orange juice blend from an equal number of pears and oranges. What percent of the blend is pear juice?
Loki, Moe, Nick and Ott are good friends. Ott had no money, but the others did. Moe gave Ott one-fifth of his money, Loki gave Ott one-fourth of his money and Nick gave Ott one-third of his money. Each gave Ott the same amount of money. What fractional part of the group's money does Ott now have?
Loki,Moe,Nick 和 Ott 是好朋友。Ott 没有钱,但其他人有。Moe 给了 Ott 五分之一的钱, Loki 给了 Ott 四分之一的钱,Nick 给了 Ott 三分之一的钱。每个人都给了 Ott 同样的钱。那么现在 Ott 有的钱占了四个人全部的钱的几分之几?
Casey's shop class is making a golf trophy. He has to paint 300 dimples on a golf ball. If it takes him 2 seconds to paint one dimple, how many minutes will he need to do his job?
On a dark and stormy night Snoopy suddenly saw a flash of lightning. Ten seconds later he heard the sound of thunder. The speed of sound is 1088 feet per second and one mile is 5280 feet. Estimate, to the nearest half-mile, how far Snoopy was from the flash of lightning.
Six trees are equally spaced along one side of a straight road. The distance from the first tree to the fourth is 60 feet. What is the distance in feet between the first and last trees?
To promote her school's annual Kite Olympics, Genevieve makes a small kite and a large kite for a bulletin board display. The kites look like the one in the diagram. For her small kite Genevieve draws the kite on a one-inch grid. For the large kite she triples both the height and width of the entire grid.
What is the number of square inches in the area of the small kite?
To promote her school's annual Kite Olympics, Genevieve makes a small kite and a large kite for a bulletin board display. The kites look like the one in the diagram. For her small kite Genevieve draws the kite on a one-inch grid. For the large kite she triples both the height and width of the entire grid.
Genevieve puts bracing on her large kite in the form of a cross connecting opposite corners of the kite. How many inches of bracing material does she need?
To promote her school's annual Kite Olympics, Genevieve makes a small kite and a large kite for a bulletin board display. The kites look like the one in the diagram. For her small kite Genevieve draws the kite on a one-inch grid. For the large kite she triples both the height and width of the entire grid.
The large kite is covered with gold foil. The foil is cut from a rectangular piece that just covers the entire grid. How many square inches of waste material are cut off from the four corners?
2001 AMC8 #13 · Counting, Probability & Statistics · ★★★
Of the 36 students in Richelle's class, 12 prefer chocolate pie, 8 prefer apple, and 6 prefer blueberry. Half of the remaining students prefer cherry pie and half prefer lemon. For Richelle's pie graph showing this data, how many degrees should she use for cherry pie?
2001 AMC8 #14 · Counting, Probability & Statistics · ★★★
Tyler has entered a buffet line in which he chooses one kind of meat, two different vegetables and one dessert. If the order of food items is not important, how many different meals might he choose?
Homer began peeling a pile of 44 potatoes at the rate of 3 potatoes per minute. Four minutes later Christen joined him and peeled at the rate of 5 potatoes per minute. When they finished, how many potatoes had Christen peeled?
A square piece of paper, 4 inches on a side, is folded in half vertically. Both layers are then cut in half parallel to the fold. Three new rectangles are formed, a large one and two small ones. What is the ratio of the perimeter of one of the small rectangles to the perimeter of the large rectangle?
For the game show Who Wants To Be A Millionaire?, the dollar values of each question are shown in the table below (where K = 1000). Between which two questions is the percent increase of the value the smallest?
Car M traveled at a constant speed for a given time. This is shown by the dashed line. Car N traveled at twice the speed for the same distance. If Car M and Car N's speed and time are shown as solid line, which graph illustrates this?
汽车 M 在给定的时间内以恒定的速度行驶,其速度和时间曲线用虚线所示。汽车 N 以两倍的速度行驶了相同的距离。如果 N 车的速度和时间曲线用实线表示,则下面哪张图表说明了这一点?
2001 AMC8 #20 · Counting, Probability & Statistics · ★★★
Kaleana shows her test score to Quay, Marty and Shana, but the others keep theirs hidden. Quay thinks, "At least two of us have the same score." Marty thinks, "I didn't get the lowest score." Shana thinks, "I didn't get the highest score." List the scores from lowest to highest for Marty (M), Quay (Q) and Shana (S).
On a twenty-question test, each correct answer is worth 5 points, each unanswered question is worth 1 point and each incorrect answer is worth 0 points. Which of the following scores is NOT possible?
Points R , S and T are vertices of an equilateral triangle, and points X , Y and Z are midpoints of its sides. How many noncongruent triangles can be drawn using any three of these six points as vertices?
点 R,S 和 T 是一个等边三角形的三个顶点,点 X,Y 和 Z 分别是边的中点。使用这六个点中的任意三个作为顶点,可以画出多少个不全等的三角形?
2001 AMC8 #24 · Counting, Probability & Statistics · ★★★★
Each half of this figure is composed of 3 red triangles, 5 blue triangles and 8 white triangles. When the upper half is folded down over the centerline, 2 pairs of red triangles coincide, as do 3 pairs of blue triangles. There are 2 red-white pairs. How many white pairs coincide?
There are 24 four-digit whole numbers that use each of the four digits 2, 4, 5 and 7 exactly once. Only one of these four-digit numbers is a multiple of another one. Which of the following is it?
2000 AMC8 #4 · Counting, Probability & Statistics · ★
In 1960 only 5% of the working adults in Carlin City worked at home. By 1970 the "at-home" work force had increased to 8%. In 1980 there were approximately 15% working at home, and in 1990 there were 30%. The graph that best illustrates this is:
2000 AMC8 #5 · Counting, Probability & Statistics · ★★★
Each principal of Lincoln High School serves exactly one 3-year term. What is the maximum number of principals this school could have during an 8-year period?
Figure ABCD is a square. Inside this square three smaller squares are drawn with the side lengths as labeled. The area of the shaded L -shaped region is
ABCD 是个正方形。在这个正方形内画了 3 个小正方形,它们的边长如图所示。则 L 形状的阴影部分区域的面积是多少?
2000 AMC8 #8 · Counting, Probability & Statistics · ★★
Three dice with faces numbered 1 through 6 are stacked as shown. Seven of the eighteen faces are visible, leaving eleven faces hidden (back, bottom, between). The total number of dots NOT visible in this view is
Ara and Shea were once the same height. Since then Shea has grown 20% while Ara has grown half as many inches as Shea. Shea is now 60 inches tall. How tall, in inches, is Ara now?
Ara 和 Shea 以前身高一样。自那以后,Shea 身高增高了 20%,而 Ara 增长的高度是 Shea 增长高度的一半。Shea 现在身高 60 英寸,那么 Ara 现在身高是多少英寸?
2000 AMC8 #12 · Counting, Probability & Statistics · ★★★
A block wall 100 feet long and 7 feet high will be constructed using blocks that are 1 foot high and either 2 feet long or 1 foot long (no blocks may be cut). The vertical joins in the blocks must be staggered as shown, and the wall must be even on the ends. What is the smallest number of blocks needed to build this wall?
Triangles ABC , ADE , and EFG are all equilateral. Points D and G are midpoints of AC and AE , respectively. If AB = 4 , what is the perimeter of figure ABCDEFG ?
三角形 ABC,ADE 和 EFG 都是等边三角形。点 D 和 G 分别是形 ABCDEFG 的周长是多少?
In order for Mateen to walk a kilometer (1000m) in his rectangular backyard, he must walk the length 25 times or walk its perimeter 10 times. What is the area of Mateen's backyard in square meters?
Three circular arcs of radius 5 units bound the region shown. Arcs AB and AD are quarter-circles, and arc BCD is a semicircle. What is the area, in square units, of the region?
三段半径为 5 个单位长的圆弧围成图示区域。弧 AB 和 AD 均为四分之一圆,弧 BCD 是个半圆。
那么这个区域的面积是多少平方单位?
You have nine coins: a collection of pennies, nickels, dimes, and quarters having a total value of $1.02 , with at least one coin of each type. How many dimes must you have?
A cube has edge length 2 . Suppose that we glue a cube of edge length 1 on top of the big cube so that one of its faces rests entirely on the top face of the larger cube. The percent increase in the surface area (sides, top, and bottom) from the original cube to the new solid formed is closest to
There is a list of seven numbers. The average of the first four numbers is 5 , and the average of the last four numbers is 8 . If the average of all seven numbers is 674 , then the number common to both sets of four numbers is
A rectangular garden 60 feet long and 20 feet wide is enclosed by a fence. To make the garden larger, while using the same fence, its shape is changed to a square. By how many square feet does this enlarge the garden?
1999 AMC8 #6 · Counting, Probability & Statistics · ★★
Bo, Coe, Flo, Jo, and Moe have different amounts of money. Neither Jo nor Bo has as much money as Flo. Both Bo and Coe have more than Moe. Jo has more than Moe, but less than Bo. Who has the least amount of money?
Bo、Coe、Flo、Jo 和 Moe 各自拥有不同数量的钱。Jo 和 Bo 都没有 Flo 的钱多。Bo 和 Coe 都比 Moe 的钱多。Jo 比 Moe 的钱多,但比 Bo 的钱少。谁的钱最少?
The third exit on a highway is located at milepost 40 and the tenth exit is at milepost 160. There is a service center on the highway located three-fourths of the way from the third exit to the tenth exit. At what milepost would you expect to find this service center?
Six squares are colored, front and back, (R = red, B = blue, O = orange, Y = yellow, G = green, and W = white). They are hinged together as shown, then folded to form a cube. The face opposite the white face is
1999 AMC8 #9 · Counting, Probability & Statistics · ★★
Three flower beds overlap as shown. Bed A has 500 plants, bed B has 450 plants, and bed C has 350 plants. Beds A and B share 50 plants, while beds A and C share 100. The total number of plants is
三个花坛如图所示重叠。花坛 A 有 500 株植物,花坛 B 有 450 株,花坛 C 有 350 株。花坛 A 和 B 共享 50 株,花坛 A 和 C 共享 100 株。植物的总数是
1999 AMC8 #10 · Counting, Probability & Statistics · ★★
A complete cycle of a traffic light takes 60 seconds. During each cycle the light is green for 25 seconds, yellow for 5 seconds, and red for 30 seconds. At a randomly chosen time, what is the probability that the light will NOT be green?
1999 AMC8 #11 · Counting, Probability & Statistics · ★★★
Each of the five numbers 1, 4, 7, 10, and 13 is placed in one of the five squares so that the sum of the three numbers in the horizontal row equals the sum of the three numbers in the vertical column. The largest possible value for the horizontal or vertical sum is
The ratio of the number of games won to the number of games lost (no ties) by the Middle School Middies is 11/4 . To the nearest whole percent, what percent of its games did the team lose?
1999 AMC8 #13 · Counting, Probability & Statistics · ★★★
The average age of the 40 members of a computer science camp is 17 years. There are 20 girls, 15 boys, and 5 adults. If the average age of the girls is 15 and the average age of the boys is 16, what is the average age of the adults?
1999 AMC8 #15 · Counting, Probability & Statistics · ★★★
Bicycle license plates in Flatville each contain three letters. The first is chosen from the set {C,H,L,P,R}, the second from {A,I,O}, and the third from {D,M,N,T}. When Flatville needed more license plates, they added two new letters. The new letters may both be added to one set or one letter may be added to one set and one to another set. What is the largest possible number of ADDITIONAL license plates that can be made by adding two letters?
Tori's mathematics test had 75 problems: 10 arithmetic, 30 algebra, and 35 geometry problems. Although she answered 70% of the arithmetic, 40% of the algebra, and 60% of the geometry problems correctly, she did not pass the test because she got less than 60% of the problems right. How many more problems would she have needed to answer correctly to earn a 60% passing grade?
At Central Middle School the 108 students who take the AMC 8 meet in the evening to talk about problems and eat an average of two cookies apiece. Walter and Gretel are baking Bonnie's Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists this items: 121 cups of flour, 2 eggs, 3 tablespoons butter, 43 cups sugar, and 1 package of chocolate drops. They will make only full recipes, not partial recipes. Walter can buy eggs by the half-dozen. How many half-dozens should he buy to make enough cookies? (Some eggs and some cookies may be left over.)
中央中学 108 名参加 AMC 8 的学生晚上聚会讨论题目,平均每人吃两块曲奇。Walter 和 Gretel 今年正在烤 Bonnie's Best Bar Cookies。他们的配方可以做一盘 15 块曲奇,配料表如下:121 杯面粉、2 个鸡蛋、3 汤匙黄油、43 杯糖、1 包巧克力豆。他们只做完整的配方,不做部分配方。
Walter 可以按半打买鸡蛋。他应该买多少个半打鸡蛋才能做足够的曲奇?(可能会剩下一些鸡蛋和一些曲奇。)
At Central Middle School the 108 students who take the AMC8 meet in the evening to talk about problems and eat an average of two cookies apiece. Walter and Gretel are baking Bonnie's Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists this items: 121 cups flour, 2 eggs, 3 tablespoons butter, 43 cups sugar, and 1 package of chocolate drops. They will make only full recipes, not partial recipes. They learn that a big concert is scheduled for the same night and attendance will be down 25% . How many recipes of cookies should they make for their smaller party?
中央中学 108 名参加 AMC8 的学生晚上聚会讨论题目,平均每人吃两块曲奇。Walter 和 Gretel 今年正在烤 Bonnie's Best Bar Cookies。他们的配方可以做一盘 15 块曲奇,配料表如下:121 杯面粉、2 个鸡蛋、3 汤匙黄油、43 杯糖、1 包巧克力豆。他们只做完整的配方,不做部分配方。
At Central Middle School, the 108 students who take the AMC 8 meet in the evening to talk about problems and eat an average of two cookies apiece. Hansel and Gretel are baking Bonnie's Best Bar Cookies this year. Their recipe, which makes a pan of 15 cookies, lists these items: 121 cups flour, 2 eggs, 3 tablespoons butter, 43 cups sugar, and 1 package of chocolate drops. They will make full recipes, not partial recipes. Hansel and Gretel must make enough pans of cookies to supply 216 cookies. There are 8 tablespoons in a stick of butter. How many sticks of butter will be needed? (Some butter may be leftover, of course.)
中央中学 108 名参加 AMC 8 的学生晚上聚会讨论题目,平均每人吃两块曲奇。Hansel 和 Gretel 今年正在烤 Bonnie's Best Bar Cookies。他们的配方可以做一盘 15 块曲奇,配料表如下:121 杯面粉、2 个鸡蛋、3 汤匙黄油、43 杯糖、1 包巧克力豆。他们只做完整的配方,不做部分配方。
Figure 1 is called a "stack map." The numbers tell how many cubes are stacked in each position. Fig. 2 shows these cubes, and Fig. 3 shows the view of the stacked cubes as seen from the front.
Which of the following is the front view for the stack map in Fig. 4?
In a far-off land three fish can be traded for two loaves of bread and a loaf of bread can be traded for four bags of rice. How many bags of rice is one fish worth?
Points B , D , and J are midpoints of the sides of right triangle ACG . Points K , E , I are midpoints of the sides of triangle JDG , etc. If the dividing and shading process is done 100 times (the first three are shown) and AC=CG=6 , then the total area of the shaded triangles is nearest
A child's wading pool contains 200 gallons of water. If water evaporates at the rate of 0.5 gallons per day and no other water is added or removed, how many gallons of water will be in the pool after 30 days?
For a sale, a store owner reduces the price of a $10 scarf by 20% . Later the price is lowered again, this time by one-half the reduced price. The price is now
Each of the letters W , X , Y , and Z represents a different integer in the set {1,2,3,4} , but not necessarily in that order. If XW−ZY=1 , then the sum of W and Y is
字母 W、X、Y 和 Z 各代表集合 {1,2,3,4} 中不同的整数,但不一定按此顺序。若 XW−ZY=1,则 W 与 Y 之和为
An Annville Junior High School, 30% of the students in the Math Club are in the Science Club, and 80% of the students in the Science Club are in the Math Club. There are 15 students in the Science Club. How many students are in the Math Club?
As indicated by the diagram below, a rectangular piece of paper is folded bottom to top, then left to right, and finally, a hole is punched at X. What does the paper look like when unfolded?
如下图所示,将一张矩形纸从下往上折叠,再从左往右折叠,最后在 X 处打一个孔。展开后纸张是什么样子?
1998 AMC8 #19 · Counting, Probability & Statistics · ★★★
Tamika selects two different numbers at random from the set {8,9,10} and adds them. Carlos takes two different numbers at random from the set {3,5,6} and multiplies them. What is the probability that Tamika's result is greater than Carlos' result?
Tamika 从集合 {8,9,10} 中随机选两个不同的数并相加。Carlos 从集合 {3,5,6} 中随机选两个不同的数并相乘。Tamika 的结果大于 Carlos 的结果的概率是多少?
Let PQRS be a square piece of paper. P is folded onto R and then Q is folded onto S . The area of the resulting figure is 9 square inches. Find the perimeter of square PQRS .
设 PQRS 为一张正方形纸。将 P 折到 R 上,再将 Q 折到 S 上。所得图形的面积为 9 平方英寸。求正方形 PQRS 的周长。
Terri produces a sequence of positive integers by following three rules. She starts with a positive integer, then applies the appropriate rule to the result, and continues in this fashion. Rule 1: If the integer is less than 10, multiply it by 9. Rule 2: If the integer is even and greater than 9, divide it by 2. Rule 3: If the integer is odd and greater than 9, subtract 5 from it. A sample sequence: 23,18,9,81,76,…. Find the 98th term of the sequence that begins 98,49,….
A rectangular board of 8 columns has squares numbered beginning in the upper left corner and moving left to right so row one is numbered 1 through 8, row two is 9 through 16, and so on. A student shades square 1, then skips one square and shades square 3, skips two squares and shades square 6, skips 3 squares and shades square 10, and continues in this way until there is at least one shaded square in each column. What is the number of the shaded square that first achieves this result?
Three generous friends, each with some money, redistribute the money as followed: Amy gives enough money to Jan and Toy to double each of their amounts. Jan then gives enough to Amy and Toy to double their amounts. Finally, Toy gives enough to Amy and Jan to double their amounts. If Toy had 36 dollars at the beginning and 36 dollars at the end, what is the total amount that all three friends have?
三位慷慨的朋友各自拥有一些钱,按如下方式重新分配:Amy 给 Jan 和 Toy 足够的钱,使他们各自的金额翻倍。然后 Jan 给 Amy 和 Toy 足够的钱,使他们的金额翻倍。最后,Toy 给 Amy 和 Jan 足够的钱,使他们的金额翻倍。如果 Toy 一开始有 36 美元,最后也有 36 美元,那么三位朋友共有多少钱?
Julie is preparing a speech for her class. Her speech must last between one-half hour and three-quarters of an hour. The ideal rate of speech is 150 words per minute. If Julie speaks at the ideal rate, which of the following number of words would be an appropriate length for her speech?
Walter gets up at 6:30 a.m., catches the school bus at 7:30 a.m., has 6 classes that last 50 minutes each, has 30 minutes for lunch, and has 2 hours additional time at school. He takes the bus home and arrives at 4:00 p.m. How many minutes has he spent on the bus?
Three bags of jelly beans contain 26, 28, and 30 beans. The ratios of yellow beans to all beans in each of these bags are 50% , 25% , and 20% , respectively. All three bags of candy are dumped into one bowl. Which of the following is closest to the ratio of yellow jelly beans to all beans in the bowl?
1997 AMC8 #14 · Counting, Probability & Statistics · ★★★
There is a set of five positive integers whose average (mean) is 5, whose median is 5, and whose only mode is 8. What is the difference between the largest and smallest integers in the set?
Each side of the large square in the figure is trisected (divided into three equal parts). The corners of an inscribed square are at these trisection points, as shown. The ratio of the area of the inscribed square to the area of the large square is
Penni Precisely buys $100 worth of stock in each of three companies: Alabama Almonds, Boston Beans, and California Cauliflower. After one year, AA was up 20%, BB was down 25%, and CC was unchanged. For the second year, AA was down 20% from the previous year, BB was up 25% from the previous year, and CC was unchanged. If A, B, and C are the final values of the stock, then
A cube has eight vertices (corners) and twelve edges. A segment, such as x , which joins two vertices not joined by an edge is called a diagonal. Segment y is also a diagonal. How many diagonals does a cube have?
一个正方体有八个顶点和十二条棱。像 x 这样连接两个不被棱相连的顶点的线段称为对角线。线段 y 也是一条对角线。一个正方体有多少条对角线?
At the grocery store last week, small boxes of facial tissue were priced at 4 boxes for $5 . This week they are on sale at 5 boxes for $4 . The percent decrease in the price per box during the sale was closest to
1997 AMC8 #20 · Counting, Probability & Statistics · ★★★
A pair of 8-sided dice have sides numbered 1 through 8. Each side has the same probability (chance) of landing face up. The probability that the product of the two numbers that land face-up exceeds 36 is
There are positive integers that have these properties: The sum of the squares of their digits is equal to 50 Each digit is larger than the one on it's left The product of the digits of the largest integer with both properties is
Diameter ACE is divided at C in the ratio 2:3 . The two semicircles, ABC and CDE , divide the circular region into an upper (shaded) region and a lower region. The ratio of the area of the upper region to that of the lower region is
All of the even numbers from 2 to 98 inclusive, excluding those ending in 0, are multiplied together. What is the rightmost digit (the units digit) of the product?
Jose, Thuy, and Kareem each start with the number 10 . Jose subtracts 1 from the number 10 , doubles his answer, and then adds 2 . Thuy doubles the number 10 , subtracts 1 from her answer, and then adds 2 . Kareem subtracts 1 from the number 10 , adds 2 to his number, and then doubles the result. Who gets the largest final answer?
The 64 whole numbers from 1 through 64 are written, one per square, on a checkerboard (an 8 by 8 array of 64 squares). The first 8 numbers are written in order across the first row, the next 8 across the second row, and so on. After all 64 numbers are written, the sum of the numbers in the four corners will be
What is the smallest result that can be obtained from the following process? Choose three different numbers from the set {3,5,7,11,13,17} . Add two of these numbers. Multiply their sum by the third number.
Brent has goldfish that quadruple (become four times as many) every month, and Gretel has goldfish that double every month. If Brent has 4 goldfish at the same time that Gretel has 128 goldfish, then in how many months from that time will they have the same number of goldfish?
Points A and B are 10 units apart. Points B and C are 4 units apart. Points C and D are 3 units apart. If A and D are as close as possible, then the number of units between them is
点 A 和 B 相距 10 个单位。点 B 和 C 相距 4 个单位。点 C 和 D 相距 3 个单位。如果 A 和 D 尽可能接近,则它们之间的距离是多少个单位?
When Walter drove up to the gasoline pump, he noticed that his gasoline tank was 1/8 full. He purchased 7.5 gallons of gasoline for 10 dollars. With this additional gasoline, his gasoline tank was then 5/8 full. The number of gallons of gasoline his tank holds when it is full is
In the fall of 1996, a total of 800 students participated in an annual school clean-up day. The organizers of the event expect that in each of the years 1997, 1998, and 1999, participation will increase by 50% over the previous year. The number of participants the organizers will expect in the fall of 1999 is
are placed in the squares in the figure shown so that the sum of the entries in the vertical column is 23 and the sum of the entries in the horizontal row is 12. The sum of the six digits used is
Figure OPQR is a square. Point O is the origin, and point Q has coordinates (2,2). What are the coordinates for T so that the area of triangle PQT equals the area of square OPQR ?
NOT TO SCALE
图形 OPQR 是一个正方形。点 O 是原点,点 Q 的坐标为 (2,2)。点 T 的坐标应为何值,才能使三角形 PQT 的面积等于正方形 OPQR 的面积?
Ana's monthly salary was $2000 in May. In June she received a 20% raise. In July she received a 20% pay cut. After the two changes in June and July, Ana's monthly salary was
Ana 五月份的月薪是 $2000。六月份她获得了 20% 的加薪。七月份她的薪水被削减了 20%。经过六月和七月的两次变动后,Ana 的月薪是
1996 AMC8 #19 · Counting, Probability & Statistics · ★★★
The pie charts below indicate the percent of students who prefer golf, bowling, or tennis at East Junior High School and West Middle School. The total number of students at East is 2000 and at West, 2500. In the two schools combined, the percent of students who prefer tennis is
以下饼图显示了 East 初中和 West 中学喜欢高尔夫、保龄球或网球的学生百分比。East 共有 2000 名学生,West 共有 2500 名。两所学校合计,喜欢网球的学生的百分比是
Suppose there is a special key on a calculator that replaces the number x currently displayed with the number given by the formula 1/(1-x) . For example, if the calculator is displaying 2 and the special key is pressed, then the calculator will display -1 since 1/(1-2)=-1 . Now suppose that the calculator is displaying 5. After the special key is pressed 100 times in a row, the calculator will display
The manager of a company planned to distribute a $50 bonus to each employee from the company fund, but the fund contained $5 less than what was needed. Instead the manager gave each employee a $45 bonus and kept the remaining $95 in the company fund. The amount of money in the company fund before any bonuses were paid was
1996 AMC8 #25 · Counting, Probability & Statistics · ★★★★
A point is chosen at random from within a circular region. What is the probability that the point is closer to the center of the region than it is to the boundary of the region?
A teacher tells the class, "Think of a number, add 1 to it, and double the result. Give the answer to your partner. Partner, subtract 1 from the number you are given and double the result to get your answer." Ben thinks of 6 , and gives his answer to Sue. What should Sue's answer be?
At Clover View Junior High, one half of the students go home on the school bus. One fourth go home by automobile. One tenth go home on their bicycles. The rest walk home. What fractional part of the students walk home?
An American traveling in Italy wishes to exchange American money (dollars) for Italian money (lire). If 3000 lire = 1.60, how much lire will the traveler receive in exchange for 1.00?
Three congruent circles with centers P , Q , and R are tangent to the sides of rectangle ABCD as shown. The circle centered at Q has diameter 4 and passes through points P and R . The area of the rectangle is
A jacket and a shirt originally sold for 80 dollars and 40 dollars, respectively. During a sale Chris bought the 80 dollar jacket at a 40% discount and the 40 dollar shirt at a 55% discount. The total amount saved was what percent of the total of the original prices?
Jane can walk any distance in half the time it takes Hector to walk the same distance. They set off in opposite directions around the outside of the 18-block area as shown. When they meet for the first time, they will be closest to
Jane 走任何距离所花的时间是 Hector 走同样距离所花时间的一半。他们从如图所示的 18 个街区区域的外围向相反方向出发。当他们第一次相遇时,他们最接近哪里?
A lucky year is one in which at least one date, when written in the form month/day/year, has the following property: The product of the month times the day equals the last two digits of the year. For example, 1956 is a lucky year because it has the date and 7×8=56 . Which of the following is NOT a lucky year?
A team won 40 of its first 50 games. How many of the remaining 40 games must this team win so it will have won exactly 70 % of its games for the season?
Students from three middle schools worked on a summer project. Seven students from Allen school worked for 3 days. Four students from Balboa school worked for 5 days. Five students from Carver school worked for 9 days. The total amount paid for the students' work was 774. Assuming each student received the same amount for a day's work, how much did the students from Balboa school earn altogether?
1995 AMC8 #17 · Counting, Probability & Statistics · ★★★
The table below gives the percent of students in each grade at Annville and Cleona elementary schools. Annville has 100 students and Cleona has 200 students. In the third grade, the number of students in Annville is what percent of the number of students in Cleona?
The area of each of the four congruent L-shaped regions of this 100-inch by 100-inch square is 3/16 of the total area. How many inches long is the side of the center square?
在这个 100 英寸 × 100 英寸的正方形中,四个全等 L 形区域各占总面积的 3/16。中心正方形的边长是多少英寸?
1995 AMC8 #19 · Counting, Probability & Statistics · ★★★
The graph shows the distribution of the number of children in the families of the students in Ms. Jordan's English class. The median number of children in the family for this distribution is
1995 AMC8 #20 · Counting, Probability & Statistics · ★★★
Diana and Apollo each roll a standard die obtaining a number at random from 1 to 6 . What is the probability that Diana's number is larger than Apollo's number?
Diana 和 Apollo 各自掷一个标准骰子,随机得到 1 到 6 中的一个数。Diana 的数大于 Apollo 的数的概率是多少?
A plastic snap-together cube has a protruding snap on one side and receptacle holes on the other five sides as shown. What is the smallest number of these cubes that can be snapped together so that only receptacle holes are showing?
In parallelogram ABCD , DE is the altitude to the base AB and DF is the altitude to the base BC . [Note: Both pictures represent the same parallelogram.] If DC=12 , EB=4 , and DE=6 , then DF=
在平行四边形 ABCD 中,DE 是底边 AB 上的高,DF 是底边 BC 上的高。[注:两幅图表示同一平行四边形。] 若 DC=12,EB=4,DE=6,则 DF=
Buses from Dallas to Houston leave every hour on the hour. Buses from Houston to Dallas leave every hour on the half hour. The trip from one city to the other takes 5 hours. Assuming the buses travel on the same highway, how many Dallas-bound buses does a Houston-bound bus pass in the highway (not in the station)?
Each day Maria must work 8 hours. This does not include the 45 minutes she takes for lunch. If she begins working at 7:25 A.M. and takes her lunch break at noon, then her working day will end at
Maria 每天需要工作 8 小时,不包括 45 分钟的午休时间。如果她于上午 7:25 开始工作,并在中午开始午休,那么她的工作日将结束于
A shopper buys a 100 dollar coat on sale for 20% off. An additional 5 dollars are taken off the sale price by using a discount coupon. A sales tax of 8% is paid on the final selling price. The total amount the shopper pays for the coat is
1994 AMC8 #11 · Counting, Probability & Statistics · ★★★
Last summer 100 students attended basketball camp. Of those attending, 52 were boys and 48 were girls. Also, 40 students were from Jonas Middle School and 60 were from Clay Middle School. Twenty of the girls were from Jonas Middle School. How many of the boys were from Clay Middle School?
去年夏天 100 名学生参加了篮球夏令营。参加者中 52 名男生,48 名女生。另有 40 名来自 Jonas 中学,60 名来自 Clay 中学。女生中有 20 名来自 Jonas 中学。男生中有多少名来自 Clay 中学?
Each of the three large squares shown below is the same size. Segments that intersect the sides of the squares intersect at the midpoints of the sides. How do the shaded areas of these squares compare?
Two children at a time can play pairball. For 90 minutes, with only two children playing at time, five children take turns so that each one plays the same amount of time. The number of minutes each child plays is
The perimeter of one square is 3 times the perimeter of another square. The area of the larger square is how many times the area of the smaller square?
Pauline Bunyan can shovel snow at the rate of 20 cubic yards for the first hour, 19 cubic yards for the second, 18 for the third, etc., always shoveling one cubic yard less per hour than the previous hour. If her driveway is 4 yards wide, 10 yards long, and covered with snow 3 yards deep, then the number of hours it will take her to shovel it clean is closest to
Mike leaves home and drives slowly east through city traffic. When he reaches the highway he drives east more rapidly until he reaches the shopping mall where he stops. He shops at the mall for an hour. Mike returns home by the same route as he came, driving west rapidly along the highway and then slowly through city traffic. Each graph shows the distance from home on the vertical axis versus the time elapsed since leaving home on the horizontal axis. Which graph is the best representation of Mike's trip?
Mike 离开家,在城市交通中向东缓慢行驶。当他到达高速公路上时,他更快速地向东行驶,直到到达购物中心并停下来。他在购物中心购物一小时。Mike 按原路返回,沿高速公路快速向西行驶,然后缓慢通过城市交通到达家。每个图表的纵轴表示离家距离,横轴表示离家后经过的时间。哪张图能最好地表示 Mike 的行程?
Around the outside of a 4 by 4 square, construct four semicircles (as shown in the figure) with the four sides of the square as their diameters. Another square, ABCD , has its sides parallel to the corresponding sides of the original square, and each side of ABCD is tangent to one of the semicircles. The area of the square ABCD is
Let W,X,Y and Z be four different digits selected from the set {1,2,3,4,5,6,7,8,9}. If the sum XW+ZY is to be as small as possible, then XW+ZY must equal
1994 AMC8 #21 · Counting, Probability & Statistics · ★★★
A gumball machine contains 9 red, 7 white, and 8 blue gumballs. The least number of gumballs a person must buy to be sure of getting four gumballs of the same color is
1994 AMC8 #24 · Counting, Probability & Statistics · ★★★★
A 2 by 2 square is divided into four 1 by 1 squares. Each of the small squares is to be painted either green or red. In how many different ways can the painting be accomplished so that no green square shares its top or right side with any red square? There may be as few as zero or as many as four small green squares.
A can of soup can feed 3 adults or 5 children. If there are 5 cans of soup and 15 children are fed, then how many adults would the remaining soup feed?
To control her blood pressure, Jill's grandmother takes one half of a pill every other day. If one supply of medicine contains 60 pills, then the supply of medicine would last approximately
1993 AMC8 #13 · Counting, Probability & Statistics · ★★★
The word "HELP" in block letters is painted in black with strokes 1 unit wide on a 5 by 15 rectangular white sign with dimensions as shown. The area of the white portion of the sign, in square units, is
Square corners, 5 units on a side, are removed from a 20 unit by 30 unit rectangular sheet of cardboard. The sides are then folded to form an open box. The surface area, in square units, of the interior of the box is
1993 AMC8 #22 · Counting, Probability & Statistics · ★★★★
Pat Peano has a collection of numbers to label the pages of his scrapbook. He has an infinite number of 0's, 1's, 3's, 4's, 5's, 6's, 7's, 8's and 9's, but only twenty-two 2's. How far can he number the pages of his scrapbook with these digits?
Pat Peano 有一批数字用于给他的剪贴簿页码编号。他有无限多个 0、1、3、4、5、6、7、8 和 9,但只有二十二个 2。用这些数字他最多能将剪贴簿页码编到多少?
1993 AMC8 #23 · Counting, Probability & Statistics · ★★★★
Five runners, P , Q , R , S , T , have a race, and P beats Q , P beats R , Q beats S , and T finishes after P and before Q . Who could NOT have finished third in the race?
A checkerboard consists of one-inch squares. A square card, 1.5 inches on a side, is placed on the board so that it covers part or all of the area of each of n squares. The maximum possible value of n is
棋盘由边长为 1 英寸的方格组成。一张边长为 1.5 英寸的正方形卡片放在棋盘上,使其覆盖 n 个方格的部分或全部面积。n 的最大可能值是
During the softball season, Judy had 35 hits. Among her hits were 1 home run, 1 triple and 5 doubles. The rest of her hits were single. What percent of her hits were single?
A store owner bought 1500 pencils at $ 0.10 each. If he sells them for $ 0.25 each, how many of them must he sell to make a profit of exactly $ 100.00 ?
1992 AMC8 #9 · Counting, Probability & Statistics · ★★
The population of a small town is 480 . The graph indicates the number of females and males in the town, but the vertical scale-values are omitted. How many males live in the town?
The five tires of a car (four road tires and a full-sized spare) were rotated so that each tire was used the same number of miles during the first 30,000 miles the car traveled. For how many miles was each tire used?
1992 AMC8 #13 · Counting, Probability & Statistics · ★★★
Five test scores have a mean (average score) of 90 , a median (middle score) of 91 and a mode (most frequent score) of 94 . The sum of the two lowest test scores is
On a trip, a car traveled 80 miles in an hour and a half, then was stopped in traffic for 30 minutes, then traveled 100 miles during the next 2 hours. What was the car's average speed in miles per hour for the 4 -hour trip?
1992 AMC8 #19 · Counting, Probability & Statistics · ★★★
The distance between the 5th and 26th exits on an interstate highway is 118 miles. If any two consecutive exits are at least 5 miles apart, then what is the largest number of miles there can be between two consecutive exits that are between the 5th and 26th exits?
1992 AMC8 #21 · Counting, Probability & Statistics · ★★★
Northside's Drum and Bugle Corps raised money for a trip. The drummers and bugle players kept separate sales records. According to the double bar graph, in what month did one group's sales exceed the other's by the greatest percent?
Eight 1×1 square tiles are arranged as shown so their outside edges form a polygon with a perimeter of 14 units. Two additional tiles of the same size are added to the figure so that at least one side of each tile is shared with a side of one of the squares in the original figure. Which of the following could be the perimeter of the new figure?
One half of the water is poured out of a full container. Then one third of the remainder is poured out. Continue the process: one fourth of the remainder for the third pouring, one fifth of the remainder for the fourth pouring, etc. After how many pourings does exactly one tenth of the original water remain?
A "domino" is made up of two small squares: Which of the "checkerboards" illustrated below CANNOT be covered exactly and completely by a whole number of non-overlapping dominoes?
1991 AMC8 #14 · Counting, Probability & Statistics · ★★★
Several students are competing in a series of three races. A student earns 5 points for winning a race, 3 points for finishing second and 1 point for finishing third. There are no ties. What is the smallest number of points that a student must earn in the three races to be guaranteed of earning more points than any other student?
All six sides of a rectangular solid were rectangles. A one-foot cube was cut out of the rectangular solid as shown. The total number of square feet in the surface of the new solid is how many more or less than that of the original solid?
The 16 squares on a piece of paper are numbered as shown in the diagram. While lying on a table, the paper is folded in half four times in the following sequence:
1991 AMC8 #17 · Counting, Probability & Statistics · ★★★
An auditorium with 20 rows of seats has 10 seats in the first row. Each successive row has one more seat than the previous row. If students taking an exam are permitted to sit in any row, but not next to another student in that row, then the maximum number of students that can be seated for an exam is
1991 AMC8 #18 · Counting, Probability & Statistics · ★★★
The vertical axis indicates the number of employees, but the scale was accidentally omitted from this graph. What percent of the employees at the Gauss company have worked there for 5 years or more?
For every 3∘ rise in temperature, the volume of a certain gas expands by 4 cubic centimeters. If the volume of the gas is 24 cubic centimeters when the temperature is 32∘ , what was the volume of the gas in cubic centimeters when the temperature was 20∘ ?
1991 AMC8 #22 · Counting, Probability & Statistics · ★★★
Each spinner is divided into 3 equal parts. The results obtained from spinning the two spinners are multiplied. What is the probability that this product is an even number?
1991 AMC8 #23 · Counting, Probability & Statistics · ★★★★
The Pythagoras High School band has 100 female and 80 male members. The Pythagoras High School orchestra has 80 female and 100 male members. There are 60 females who are members in both band and orchestra. Altogether, there are 230 students who are in either band or orchestra or both. The number of males in the band who are NOT in the orchestra is
A cube of edge 3 cm is cut into N smaller cubes, not all the same size. If the edge of each of the smaller cubes is a whole number of centimeters, then N=
一个棱长为 3 cm 的正方体被切成 N 个小正方体,不全部大小相同。如果每个小正方体的棱长都是整数厘米,则 N=
An equilateral triangle is originally painted black. Each time the triangle is changed, the middle fourth of each black triangle turns white. After five changes, what fractional part of the original area of the black triangle remains black?
1990 AMC8 #1 · Counting, Probability & Statistics · ★★
What is the smallest sum of two 3 -digit numbers that can be obtained by placing each of the six digits 4,5,6,7,8,9 in one of the six boxes in this addition problem?
1990 AMC8 #9 · Counting, Probability & Statistics · ★★
The grading scale shown is used at Jones Junior High. The fifteen scores in Mr. Freeman's class were: 89, 72, 54, 97, 77, 92, 85, 74, 75, 63, 84, 65, 76, 64, 67. In Mr. Freeman's class, what percent of the students received a grade of C?
On this monthly calendar, the date behind one of the letters is added to the date behind C. If this sum equals the sum of the dates behind A and B, then the letter is
在这张月历上,其中一个字母背后的日期与 C 背后的日期相加。如果这个和等于 A 和 B 背后日期之和,则该字母是
The numbers on the faces of this cube are consecutive whole numbers. The sum of the two numbers on each of the three pairs of opposite faces are equal. The sum of the six numbers on this cube is
1990 AMC8 #12 · Counting, Probability & Statistics · ★★★
There are twenty-four 4-digit numbers that use each of the four digits 2, 4, 5, and 7 exactly once. Listed in numerical order from smallest to largest, the number in the 17th position in the list is
One proposal for new postage rates for a letter was 30¢ for the first ounce and 22¢ for each additional ounce (or fraction of an ounce). The postage for a letter weighing 4.5 ounces was
1990 AMC8 #14 · Counting, Probability & Statistics · ★★★
A bag contains only blue balls and green balls. There are 6 blue balls. If the probability of drawing a blue ball at random from this bag is 41 , then the number of green balls in the bag is
A straight concrete sidewalk is to be 3 feet wide, 60 feet long, and 3 inches thick. How many cubic yards of concrete must a contractor order for the sidewalk if concrete must be ordered in a whole number of cubic yards?
1990 AMC8 #20 · Counting, Probability & Statistics · ★★★
The annual incomes of 1,000 families range from $8200 to $98,000 . In error, the largest income was entered on the computer as $980,000 . The difference between the mean of the incorrect data and the mean of the actual data is
A list of 8 numbers is formed by beginning with two given numbers. Each new number in the list is the product of the two previous numbers. Find the first number if the last three are shown:
Several students are seated at a large circular table. They pass around a bag containing 100 pieces of candy. Each person receives the bag, takes one piece of candy and then passes the bag to the next person. If Chris takes the first and last piece of candy, then the number of students at the table could be
几名学生围坐在一张大圆桌旁。他们传一袋装有 100 颗糖果的袋子。每人接过袋子,取一颗糖果,然后将袋子传给下一个人。如果 Chris 拿走第一颗也是最后一颗糖果,则桌旁的学生人数可能是
The graph relates the distance traveled [in miles] to the time elapsed [in hours] on a trip taken by an experimental airplane. During which hour was the average speed of this airplane the largest?
1990 AMC8 #25 · Counting, Probability & Statistics · ★★★★
How many different patterns can be made by shading exactly two of the nine squares? Patterns that can be matched by flips and/or turns are not considered different. For example, the patterns shown below are not considered different.
Many calculators have a reciprocal key x1 that replaces the current number displayed with its reciprocal. For example, if the display is 00004 and the x1 key is depressed, then the display becomes 000.25 . If 00032 is currently displayed, what is the fewest number of times you must depress the x1 key so the display again reads 00032 ?
1989 AMC8 #19 · Counting, Probability & Statistics · ★★★
The graph below shows the total accumulated dollars (in millions) spent by the Surf City government during 1988 . For example, about 0.5 million had been spent by the beginning of February and approximately 2 million by the end of April. Approximately how many millions of dollars were spent during the summer months of June, July, and August?
下图显示了 1988 年 Surf City 政府累计支出总额(百万美元)。例如,到二月初已支出约 0.5 百万美元,到四月底约 2 百万美元。六月、七月和八月的夏季大约支出了多少百万美元?
The figure may be folded along the lines shown to form a number cube. Three number faces come together at each corner of the cube. What is the largest sum of three numbers whose faces come together at a corner?
Jack had a bag of 128 apples. He sold 25% of them to Jill. Next he sold 25% of those remaining to June. Of those apples still in his bag, he gave the shiniest one to his teacher. How many apples did Jack have then?
Jack 有一袋 128 个苹果。他将其中的 25% 卖给了 Jill。接着他将剩下苹果中的 25% 卖给了 June。然后从袋中剩下的苹果中,他把最亮的那一个送给了老师。那时 Jack 还有多少个苹果?
An artist has 14 cubes, each with an edge of 1 meter. She stands them on the ground to form a sculpture as shown. She then paints the exposed surface of the sculpture. How many square meters does she paint?
Suppose a square piece of paper is folded in half vertically. The folded paper is then cut in half along the dashed line. Three rectangles are formed-a large one and two small ones. What is the ratio of the perimeter of one of the small rectangles to the perimeter of the large rectangle?
1989 AMC8 #25 · Counting, Probability & Statistics · ★★★★
Every time these two wheels are spun, two numbers are selected by the pointers. What is the probability that the sum of the two selected numbers is even?
Betty used a calculator to find the product 0.075×2.56 . She forgot to enter the decimal points. The calculator showed 19200 . If Betty had entered the decimal points correctly, the answer would have been
Suppose the estimated 20 billion dollar cost to send a person to the planet Mars is shared equally by the 250 million people in the U.S. Then each person's share is
1988 AMC8 #16 · Counting, Probability & Statistics · ★★★
Placing no more than one X in each small square, what is the greatest number of X 's that can be put on the grid shown without getting three X 's in a row vertically, horizontally, or diagonally?
Problem The glass gauge on a cylindrical coffee maker shows that there are 45 cups left when the coffee maker is 36% full. How many cups of coffee does it hold when it is full?
1988 AMC8 #21 · Counting, Probability & Statistics · ★★★★
A fifth number, n , is added to the set {3,6,9,10} to make the mean of the set of five numbers equal to its median. The number of possible values of n is
将第五个数 n 加入集合 {3,6,9,10} 中,使得这五个数的平均数等于其中位数。n 的可能值有多少个?
Tom's Hat Shoppe increased all original prices by 25% . Now the shoppe is having a sale where all prices are 20% off these increased prices. Which statement best describes the sale price of an item?
Tom's Hat Shoppe 将所有原价提高 25%。现在该店正在进行促销,所有价格在提高后的基础上打 20% 折扣。以下哪句话最能描述商品的促销价格?
Maria buys computer disks at a price of 4 for $5 and sells them at a price of 3 for $5 . How many computer disks must she sell in order to make a profit of $100 ?
The square in the first diagram "rolls" clockwise around the fixed regular hexagon until it reaches the bottom. In which position will the solid triangle be in diagram 4 ?
1988 AMC8 #25 · Counting, Probability & Statistics · ★★★★
A palindrome is a whole number that reads the same forwards and backwards. If one neglects the colon, certain times displayed on a digital watch are palindromes. Three examples are: 1:01, 4:44, and 12:21. How many times during a 12-hour period will be palindromes?
The large cube shown is made up of 27 identical sized smaller cubes. For each face of the large cube, the opposite face is shaded the same way. The total number of smaller cubes that must have at least one face shaded is
If the letters are replaced by digits so that the given addition problem is correct, then the number of digits (not necessarily different) in the sum of the three whole numbers is
The sale ad read: "Buy three tires at the regular price and get the fourth tire for $3. " Sam paid $240 for a set of four tires at the sale. What was the regular price of one tire?
促销广告写道:"以原价购买三个轮胎,第四个轮胎仅需 $3。" Sam 在促销中以 $240 买了一套四个轮胎。一个轮胎的原价是多少?
Joyce made 12 of her first 30 shots in the first three games of this basketball season, so her seasonal shooting average was 40% . In her next game, she took 10 shots and raised her seasonal shooting average to 50% . How many of these 10 shots did she make?
1987 AMC8 #17 · Counting, Probability & Statistics · ★★★
Abby, Bret, Carl, and Dana are seated in a row of four seats numbered #1 to #4 . Joe looks at them and says: "Bret is next to Carl." "Abby is between Bret and Carl." However each one of Joe's statements is false. Bret is actually sitting in seat #3 . Who is sitting in seat #2 ?
Abby、Bret、Carl 和 Dana 坐在编号为 #1 到 #4 的四个座位上。Joe 看着他们说:
Half the people in a room left. One third of those remaining started to dance. There were then 12 people who were not dancing. The original number of people in the room was
A calculator has a squaring key x2 which replaces the current number displayed with its square. For example, if the display is 3 and the x2 key is depressed, then the display becomes 9 . If the display reads 2 , how many times must you depress the x2 key to produce a displayed number greater than 500 ?
Suppose n∗ means n1 , the reciprocal of n . For example, 5∗=51 . How many of the following statements are true? i) 3∗+6∗=9∗ ii) 6∗−4∗=2∗ iii) 2∗⋅6∗=12∗ iv) 10∗÷2∗=5∗
1987 AMC8 #23 · Counting, Probability & Statistics · ★★★
The table below gives the 1980 U.S. population for each of the four geographic regions and for each of two ethnic groups. To the nearest percent, what percent of the U.S. Black population lived in the South?
A multiple choice examination consists of 20 questions. The scoring is +5 for each correct answer, -2 for each incorrect answer, and 0 for each unanswered question. John's score on the examination is 48 . What is the maximum number of questions he could have answered correctly?
1987 AMC8 #25 · Counting, Probability & Statistics · ★★★★
Ten balls numbered 1 to 10 are in a jar. Jack reaches into the jar and randomly removes one of the balls. Then Jill reaches into the jar and randomly removes a different ball. The probability that the sum of the two numbers on the balls removed is even is
A picture 3 feet across is hung in the center of a wall that is 19 feet wide. How many feet from the end of the wall is the nearest edge of the picture?
1986 AMC8 #12 · Counting, Probability & Statistics · ★★★
Problem The table below displays the grade distribution of the 30 students in a mathematics class on the last two tests. For example, exactly one student received a 'D' on Test 1 and a 'C' on Test 2 (see circled entry). What percent of the students received the same grade on both tests?
Sale prices at the Ajax Outlet Store are 50% below original prices. On Saturdays an additional discount of 20% off the sale price is given. What is the Saturday price of a coat whose original price is \textdollar180?
1986 AMC8 #16 · Counting, Probability & Statistics · ★★★
A bar graph shows the number of hamburgers sold by a fast food chain each season. However, the bar indicating the number sold during the winter is covered by a smudge. If exactly 25% of the chain's hamburgers are sold in the fall, how many million hamburgers are sold in the winter?
1986 AMC8 #18 · Counting, Probability & Statistics · ★★★
A rectangular grazing area is to be fenced off on three sides using part of a 100 meter rock wall as the fourth side. Fence posts are to be placed every 12 meters along the fence including the two posts where the fence meets the rock wall. What is the fewest number of posts required to fence an area 36 m by 60 m?
一块矩形放牧区需用围墙三面围起,以一段 100 米的石墙作为第四边。围墙柱每隔 12 米竖一根,包括围墙与石墙相接处的两根柱子。围起 36 m × 60 m 的区域最少需要多少根柱子?
At the beginning of a trip, the mileage odometer read 56,200 miles. The driver filled the gas tank with 6 gallons of gasoline. During the trip, the driver filled his tank again with 12 gallons of gasoline when the odometer read 56,560 . At the end of the trip, the driver filled his tank again with 20 gallons of gasoline. The odometer read 57,060 . To the nearest tenth, what was the car's average miles-per-gallon for the entire trip?
Suppose one of the eight lettered identical squares is included with the four squares in the T-shaped figure outlined. How many of the resulting figures can be folded into a topless cubical box?
假设八个标有字母的全等正方形之一与 T 形外框中的四个正方形合并。所得图形中有多少个可以折叠成一个无盖的正方体盒子?
1986 AMC8 #22 · Counting, Probability & Statistics · ★★★★
Alan, Beth, Carlos, and Diana were discussing their possible grades in mathematics class this grading period. Alan said, "If I get an A, then Beth will get an A." Beth said, "If I get an A, then Carlos will get an A." Carlos said, "If I get an A, then Diana will get an A." All of these statements were true, but only two of the students received an A. Which two received A's?
The large circle has diameter AC . The two small circles have their centers on AC and just touch at O , the center of the large circle. If each small circle has radius 1 , what is the value of the ratio of the area of the shaded region to the area of one of the small circles?
大圆的直径为 AC。两个小圆的圆心在 AC 上,且恰好在 O 点(大圆的圆心)相切。如果每个小圆的半径为 1,着色区域与一个小圆的面积之比是多少?
1986 AMC8 #24 · Counting, Probability & Statistics · ★★★★
The 600 students at King Middle School are divided into three groups of equal size for lunch. Each group has lunch at a different time. A computer randomly assigns each student to one of three lunch groups. The probability that three friends, Al, Bob, and Carol, will be assigned to the same lunch group is approximately
King 中学的 600 名学生被平均分成三组用午餐。每组在不同的时间用餐。一台计算机随机将每名学生分配到三个午餐组之一。三个朋友 Al、Bob 和 Carol 被分到同一午餐组的概率大约是
1985 AMC8 #5 · Counting, Probability & Statistics · ★
The bar graph shows the grades in a mathematics class for the last grading period. If A, B, C, and D are satisfactory grades, what fraction of the grades shown in the graph are satisfactory?
柱状图显示了一个数学班上个评分周期的成绩。如果 A、B、C 和 D 是及格成绩,图表中显示的及格成绩占几分之几?
A "stair-step" figure is made of alternating black and white squares in each row. Rows 1 through 4 are shown. All rows begin and end with a white square. The number of black squares in the 37th row is
A piece of paper containing six joined squares labeled as shown in the diagram is folded along the edges of the squares to form a cube. The label of the face opposite the face labeled X is
一张纸上有六个相连的正方形,标记如图所示。将纸沿正方形的边折叠形成一个正方体。与面 X 相对的面上的标记是
If you walk for 45 minutes at a rate of 4 mph and then run for 30 minutes at a rate of 10 mph , how many miles will you have gone at the end of one hour and 15 minutes?
If your average score on your first six mathematics tests was 84 and your average score on your first seven mathematics tests was 85, then your score on the seventh test was
Nine copies of a certain pamphlet cost less than $10.00 while ten copies of the same pamphlet (at the same price) cost more than $11.00. How much does one copy of this pamphlet cost?
1985 AMC8 #22 · Counting, Probability & Statistics · ★★★★
Assume every 7-digit whole number is a possible telephone number except those that begin with 0 or 1 . What fraction of telephone numbers begin with 9 and end with 0 ?
King Middle School has 1200 students. Each student takes 5 classes a day. Each teacher teaches 4 classes. Each class has 30 students and 1 teacher. How many teachers are there at King Middle School?
1985 AMC8 #24 · Counting, Probability & Statistics · ★★★★
In a magic triangle, each of the six whole numbers 10-15 is placed in one of the circles so that the sum, S , of the three numbers on each side of the triangle is the same. The largest possible value for S is
在一个魔力三角形中,六个整数 10-15 各放入一个圆圈,使得三角形每条边上的三个数之和 S 相同。S 的最大可能值是
1985 AMC8 #25 · Counting, Probability & Statistics · ★★★★
Five cards are lying on a table as shown. Each card has a letter on one side and a whole number on the other side. Jane said, "If a vowel is on one side of any card, then an even number is on the other side." Mary showed Jane was wrong by turning over one card. Which card did Mary turn over?
如图所示,桌上放着五张卡片。每张卡片一面是字母、另一面是整数。Jane 说:「如果任何一张卡片的一面是元音字母,那么它的另一面就是偶数。」Mary 只翻开一张卡片就证明了 Jane 是错的。Mary 翻开的是哪张卡片?