AMC 8 2005 Problem 1

AMC8 2005 年第 1 题

表达式与运算★☆☆☆☆

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?

Connie 把一个数字乘以 2，得到答案为 60。然而，她本应该把数字除以 2 才能得到正确的答案。那么正确答案是什么？

A.7.5
B.15
C.30
D.120
E.240

正确答案 · Correct Answer

解析 · Solution

Solution 1

x

is the number, then 2x=60 and x=30. Dividing the number by 2 yields

\dfrac{30}{2} = 15

. A second way to do it is to divide the number by 4, as you multiplied by 2 when you were supposed to divide by 2. So,

\dfrac{60}{4} = 15

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