2015 AMC 10A Problem 5

Question

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

Concepts:mean

Total score equals the average times the number of graded tests

Subtract the first

14

students’ total from the full class total

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.

Problem 5 in other years