Question

A 房间里 $6$ 个人的平均年龄是 $40$ 。B 房间里 $4$ 个人的平均年龄是 $25$ 。如果把两组人合在一起，所有人的平均年龄是多少？

The average age of the $6$ people in Room A is $40.$ The average age of the $4$ people in Room B is $25.$ If the two groups are combined, what is the average age of all the people?

$\ 32.5$

$\ 33$

$\ 33.5$

$\ 34$

$\ 35$

答案：D

知识点：平均数

难度评级：960

解答：

A 房间的年龄总和为 $6\cdot 40 = 240.$

B 房间的年龄总和为 $4\cdot 25 = 100.$

总和为 $240+100 = 340.$

因此平均年龄为 $\dfrac{340}{10} =34.$

所以正确答案是 D。

The sum of the ages in Room A is $6\cdot 40 = 240.$

The sum of the ages in Room B is $4\cdot 25 = 100.$

The total sum is $240+100 = 340.$

The average is therefore $\dfrac{340}{10} =34.$

Thus, the answer is D .

2008 AMC 8 第 10 题

答案：D

难度评级：960

解答：

其他年份的第 10 题