2015 AMC 10A 第 5 题

Question

Patrick 先生教

15

名学生数学。他批改测验时发现，在批完除 Payton 以外所有人的试卷后，全班平均分为

80

。批完 Payton 的试卷后，测验平均分变为

81

。Payton 的测验分数是多少？

Mr. Patrick teaches math to

15

students. He was grading tests and found that when he graded everyone’s test except Payton’s, the average grade for the class was

80.

After he graded Payton’s test, the class average became

81.

What was Payton’s score on the test?

81

85

91

94

95

知识点：平均数

总分等于平均分乘以已批改的试卷数。

Total score equals the average times the number of graded tests

用全班总分减去前

14

名学生的总分。

Subtract the first

14

students’ total from the full class total

前

14

份已批改试卷的总分为

14\cdot 80=1120

。

加入 Payton 的试卷后，总分为

15\cdot 81=1215

，所以 Payton 的分数为

1215-1120=95

。

所以正确答案是 E。

The total for the first

14

graded tests was

14\cdot 80=1120

.

After Payton’s test was included, the total became

15\cdot 81=1215

. Therefore Payton’s score was

1215-1120=95

.

Thus, E is the correct answer.

其他年份的第 5 题