2012 AMC 10A 第 5 题

Question

去年有

100

只成年猫被送到 Smallville 动物收容所，其中一半是母猫。成年母猫中有一半各带着一窝小猫，每窝平均有

4

只小猫。去年这个收容所一共收到多少只成年猫和小猫？

Last year

100

adult cats, half of whom were female, were brought into the Smallville Animal Shelter. Half of the adult female cats were accompanied by a litter of kittens. The average number of kittens per litter was

4.

What was the total number of cats and kittens received by the shelter last year?

150

200

250

300

400

答案：B

知识点：分数平均数

难度评级：870

小提示：

先求成年母猫的数量，再求带小猫的母猫数量。

Half the adult cats are female, and half of those have litters

大提示：

用带小猫的母猫数乘以平均每窝小猫数。

Multiply the number of litters by the average litter size

解答：

成年母猫有

100 \div 2 = 50

只，其中带小猫的有

50 \div 2 = 25

只。

因为平均每窝有

4

只小猫，所以小猫总数为

4 \cdot 25 = 100\text{。}

因此成年猫和小猫的总数为

100 + 100 = 200\text{。}

所以正确答案是 B。

We have that there are

100 \div 2 = 50

female cats. We then have that

50 \div 2 = 25

cats that have kittens.

Since the average number of kittens per litter is

4,

the total number of kittens is

4 \cdot 25 = 100.

The total number of cats and kittens is then

100 + 100 = 200.

Thus, B is the correct answer.

2012 AMC 10A 第 5 题

答案：B

难度评级：870

小提示：

大提示：

解答：

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