AMC 8 1989 Problem 17

AMC8 1989 年第 17 题

方程与不等式★★★☆☆

The number

N

is between 9 and 17 . The average of 6 , 10 , and

N

could be

数

N

在 9 到 17 之间。6、10 和

N

的平均数可能是

正确答案 · Correct Answer

解析 · Solution

Solution 1

The smallest possible average is

\displaystyle \frac{6 + 10 + 9}{3} = \frac{25}{3} = 8\frac{1}{3}

, while the highest possible average is

\displaystyle \frac{6+10+17}{3} = \frac{33}{3} = 11

. The only answer choice between

\displaystyle 8\frac{1}{3}

and 11 is 10, which would be the average if N = 14.

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