AMC 8 2016 Problem 3

AMC8 2016 年第 3 题

统计与数据图表★☆☆☆☆

Four students take an exam. Three of their scores are 70, 80, and 90 . If the average of their four scores is 70 , then what is the remaining score?

4 个学生参加一个考试。其中 3 个的分数是 70，80，90．若他们的平均分是 70 分，那么剩下那个学生的分数是多少分？

正确答案 · Correct Answer

解析 · Solution

Solution 1

Let

r

be the remaining student's score. We know that the average, 70, is equal to

\displaystyle \frac{70 + 80 + 90 + r}{4}

. We can use basic algebra to solve for

r

\displaystyle \frac{70 + 80 + 90 + r}{4} = 70

\displaystyle \frac{240 + r}{4} = 70

240 + r = 280 r = 40 giving us the answer of 40.

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