AMC 8 2006 Problem 12

AMC8 2006 年第 12 题

百分比★★★☆☆

Antonette gets 70 % on a 10-problem test, 80 % on a 20-problem test and 90 % on a 30-problem test. If the three tests are combined into one 60-problem test, which percent is closest to her overall score?

Antonette 在一场 10 道题的考试中得分为 70％，在一场 20 道题的考试中得分为 80％，在一场 30 道题的考试中得分为 90％.若这三场考试题合并成一场 60 道题的考试，那么下面哪个百分数最接近他的总分？

A.40
B.77
C.80
D.83
E.87

正确答案 · Correct Answer

解析 · Solution

Solution 1

70 \% \cdot 10=7

80 \% \cdot 20=16

90 \% \cdot 30=27

. Adding them up gets 7+16+27=50. The overall percentage correct would be

\displaystyle \frac{50}{60} = \frac{5}{6} = 5 \cdot 16.\overline{6}=83.\overline{3} \approx 83

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