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：

其他年份的第 5 题