AMC8 2003

AMC8 2003 · Q7

AMC8 2003 · Q7. It mainly tests Averages (mean), Arithmetic misc.

Blake and Jenny each took four 100-point tests. Blake averaged 78 on the four tests. Jenny scored 10 points higher than Blake on the first test, 10 points lower than him on the second test, and 20 points higher on both the third and fourth tests. What is the difference between Jenny’s average and Blake’s average on these four tests?

Blake 和 Jenny 各参加了四次满分 100 分的测试。Blake 的四次测试平均分是 78 分。Jenny 在第一次测试比 Blake 高 10 分，第二次比他低 10 分，第三次和第四次各比他高 20 分。这四次测试中，Jenny 的平均分与 Blake 的平均分的差是多少？

(A) 10 10

(B) 15 15

(D) 25 25

(E) 40 40

Answer

Correct choice: (A)

正确答案：（A）

Solution

Blake scored a total of $4 \times 78 = 312$ points on the four tests. Jenny scored $10 -10 + 20 + 20 = 40$ more points than Blake, so her average was $\frac{352}{4} = 88$, or 10 points higher than Blake’s.

Blake 四次测试总分是 $4 \times 78 = 312$ 分。Jenny 比 Blake 多得了 $10 -10 + 20 + 20 = 40$ 分，所以她的平均分是 $\frac{352}{4} = 88$ 分，比 Blake 高 10 分。

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