1983 AMC 12 第 9 题

Question

在某个人群中，女性人数与男性人数之比为

11

比

10

。若女性的平均（算术平均）年龄为

34

，男性的平均年龄为

32

，则该人群的平均年龄为

In a certain population the ratio of the number of women to the number of men is

11

to

10.

If the average (arithmetic mean) age of the women is

34

and the average age of the men is

32,

then the average age of the population is

32\frac9{10}

32\frac{20}{21}

33

33\frac1{21}

33\frac1{10}

取

11

名女性和

10

名男性

Use groups of

11

women and

10

men

用

11\cdot34+10\cdot32

除以总人数

Divide

11\cdot34+10\cdot32

by the total number of people

取

11

名女性和

10

名男性，所有人的年龄总和为

11\cdot34+10\cdot32=694

。再除以总人数

21

，得到

\frac{694}{21}=33\frac1{21}

。

所以正确答案是 D。

Using

11

women and

10

men, the total of all ages is

11\cdot34+10\cdot32=694.

Dividing by

21

people gives

\frac{694}{21}=33\frac1{21}.

Therefore, the correct answer is D.

其他年份的第 9 题