Question

应从列表

$1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11$

中去掉哪个数，使剩余数的平均数为 $6.1$ ？

What number should be removed from the list

$1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11$

so that the average of the remaining numbers is $6.1?$

$4$

$5$

$6$

$7$

$8$

$1$ 到 $11$ 的和是 $66$ 。若剩下十个数的平均数是 $6.1$ ，它们的和必须是 $10 \cdot 6.1 = 61$ 。

所以被去掉的数是 $66 - 61 = 5$ 。

所以正确答案是 B。

The sum of $1$ through $11$ is $66$ . For ten numbers to average $6.1$ , their sum must be $10 \cdot 6.1 = 61$ .

So the removed number is $66 - 61 = 5$ .

Thus, the correct answer is B .