AMC 8 2000 Problem 19

AMC8 2000 年第 19 题

圆★★★☆☆

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？ Problem 20 You have nine coins: a collection of pennies, nickels, dimes, and quarters having a total value of $, with at least one coin of each type. How many dimes must you have? 你有 9 枚硬币：若干便士，五分镍币，一角硬币和 25 分硬币，总价值是 1.02 美元，并且每种硬币都至少有一枚。那么你肯定有多少枚一角硬币？

A.25
B. $10+5\pi$
C.50
D. $50+5\pi$
E. $25\pi$

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