AMC8 1999

AMC8 1999 · Q16

AMC8 1999 · Q16. It mainly tests Percent, Averages (mean).

Tori's mathematics test had 75 problems: 10 arithmetic, 30 algebra, and 35 geometry problems. Although she answered 70% of the arithmetic, 40% of the algebra, and 60% of the geometry problems correctly, she did not pass the test because she got less than 60% of the problems right. How many more questions would she have needed to answer correctly to earn a 60% passing grade?

Tori 的数学测试共有 75 道题：10 道算术题，30 道代数题，35 道几何题。虽然她在算术题中答对了 70%，代数题中答对了 40%，几何题中答对了 60%，但她没有通过测试，因为她答对的题目不到 60%。她还需要多答对多少题才能达到 60% 的及格分数？

(A) 1 1

(B) 5 5

(D) 9 9

(E) 11 11

Answer

Correct choice: (B)

正确答案：（B）

Solution

Answer (B): Since 70%(10) + 40%(30) + 60%(35) = 7 + 12 + 21 = 40, she answered 40 questions correctly. She needed 60%(75) = 45 to pass, so she needed 5 more correct answers.

答案（B）：因为 $70\%(10) + 40\%(30) + 60\%(35) = 7 + 12 + 21 = 40$，所以她答对了 40 题。她需要 $60\%(75) = 45$ 才能通过，因此她还需要再答对 5 题。

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