Question

pairball 每次可以由两个孩子玩。 $90$ 分钟内始终只有两个孩子同时在玩，五个孩子轮流上场，使每个人玩的时间相同。每个孩子玩了多少分钟？

Two children at a time can play pairball. For $90$ minutes, with only two children playing at one time, five children take turns so that each one plays the same amount of time. The number of minutes each child plays is

$9$

$10$

$18$

$20$

$36$

答案：E

知识点：速率

难度评级：820

解答：

任意时刻都有两个孩子在玩，共 $90$ 分钟，所以总游戏时间是 $2 \times 90 = 180$ 个孩子分钟。

平均分给 $5$ 个孩子，每个孩子玩 $\dfrac{180}{5} = 36$ 分钟。

所以正确答案是 E。

Two children play at every moment for $90$ minutes, so the total playing time is $2 \times 90 = 180$ child-minutes.

Split equally among $5$ children, each plays $\dfrac{180}{5} = 36$ minutes.

Thus, the correct answer is E .

1994 AMC 8 第 14 题

答案：E

难度评级：820

解答：

其他年份的第 14 题