2012 AMC 10A 第 1 题

Question

Cagney 每

20

秒给一个纸杯蛋糕涂糖霜，Lacey 每

30

秒给一个纸杯蛋糕涂糖霜。两人一起工作，

5

分钟内可以给多少个纸杯蛋糕涂糖霜？

Cagney can frost a cupcake every

20

seconds and Lacey can frost a cupcake every

30

seconds. Working together, how many cupcakes can they frost in

5

minutes?

10

15

20

25

30

先把两人的速度都换成每分钟能完成的个数。

Convert each frosting rate to cupcakes per minute

把两个速度相加，再乘以

5

分钟。

Add the two rates, then multiply by

5

minutes

Cagney 每分钟完成

60 \div 20 = 3

个，Lacey 每分钟完成

60 \div 30 = 2

个。

5

分钟内，他们能完成

5(2 + 3) = 5 \cdot 5 = 25\text{。}

所以正确答案是 D。

Cagney can make

60 \div 20 = 3

cupcakes per minute, and Lacey can make

60 \div 30 = 2.

In

5

minutes, they can make

5(2 + 3) = 5 \cdot 5 = 25.

Thus, D is the correct answer.

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