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2015 AMC 12A Problem 3

Problem 3 of 25EasierProbability & Statistics

Mr. Patrick teaches math to 1515 students. He was grading tests and found that when he graded everyone’s test except Payton’s, the average grade for the class was 80.80. After he graded Payton’s test, the class average became 81.81. What was Payton’s score on the test?

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Solution

The sum of the 1414 other scores was 14⋅80=1120.14\cdot 80 = 1120. The sum of all 1515 scores was 15⋅81=1215.15\cdot 81 = 1215. Therefore Payton’s score was 1215−1120=95.1215 - 1120 = 95. Thus, the correct answer is E.
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