2012 AMC 12A 第 5 题

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所有题目均经美国数学协会(MAA)官方合法授权使用。

5.

一份水果沙拉由蓝莓、覆盆子、葡萄和樱桃组成。水果沙拉中共有 280280 块水果。覆盆子的数量是蓝莓的两倍,葡萄的数量是樱桃的三倍,樱桃的数量是覆盆子的四倍。水果沙拉中有多少颗樱桃?

A fruit salad consists of blueberries, raspberries, grapes, and cherries. The fruit salad has a total of 280280 pieces of fruit. There are twice as many raspberries as blueberries, three times as many grapes as cherries, and four times as many cherries as raspberries. How many cherries are there in the fruit salad?

88

1616

2525

6464

9696

答案:D
知识点:比与比例方程组
难度评级:1040
解答:

设蓝莓有 bb 颗。则覆盆子有 2b2b 颗,樱桃有 42b=8b4 \cdot 2b = 8b 颗,葡萄有 38b=24b3 \cdot 8b = 24b 颗。

总数为 b+2b+8b+24b=35b=280b + 2b + 8b + 24b = 35b = 280,所以 b=8b = 8,樱桃有 8b=648b = 64 颗。

因此,正确答案是 D

Let bb be the number of blueberries. Then there are 2b2b raspberries, 42b=8b4 \cdot 2b = 8b cherries, and 38b=24b3 \cdot 8b = 24b grapes.

The total is b+2b+8b+24b=35b=280,b + 2b + 8b + 24b = 35b = 280, so b=8b = 8 and there are 8b=648b = 64 cherries.

Thus, the correct answer is D.

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