1969 AMC 12 第 9 题

Question

从

2

开始的五十二个连续正整数的算术平均数（普通平均数）为：

The arithmetic mean (ordinary average) of the fifty-two successive positive integers beginning with

2

is:

27

27\dfrac14

27\dfrac12

28

28\dfrac12

求出数列中的第五十二个整数

Find the fifty-second integer in the list

等差数列的平均数等于首项与末项的平均数

The mean of an arithmetic sequence is the average of its first and last terms

这些整数从

2

到

2+51=53

。它们的平均数是首项与末项的平均数：

\frac{2+53}{2}=\frac{55}{2}=27\frac12\text{。}

因此，正确答案是 C。

The integers run from

2

through

2+51=53.

Their mean is the average of the first and last:

\frac{2+53}{2}=\frac{55}{2}=27\frac12.

Therefore, the correct answer is C.

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