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Source: Official Guide for the GMAT 13th Ed. Problem Solving; #30 Official Guide for the GMAT 2015 14th Ed. Problem Solving; #30

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A students average (arithmetic mean) test score

A students average (arithmetic mean) test score on 4 tests is 78. What must be the student's score on a 5th test for the student's average score on the 5 tests to be 80?

2 Explanations

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1

Chitrabhanu Dasgupta

I thought in a different way:
To reach an avg of 80, 4 guys are lacking { (80 - 78) * 4 } number i.e. 8 numbers

5th guy must score this extra numbers along with his 80 to cover the deficit i.e. 80 + 8 = 88

Feb 7, 2016 • Comment

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2

Gravatar Mike McGarry, Magoosh Tutor

Dec 27, 2013 • Comment

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