SOLUTION: The average score on kims first 4 tests is 78. Her score on her 5th test raises her average for all 5 tests to 81 what was her score on her 5th test?

Question 698875: The average score on kims first 4 tests is 78. Her score on her 5th test raises her average for all 5 tests to 81 what was her score on her 5th test?
Answer by Simnepi(216) (Show Source): You can put this solution on YOUR website!
Kim's total score on the first 4 tests must have been 4*78 for her to get a mean score of 78. We don't know what the individual scores were, we just know that the total was 312 (4*78).
For KIm to average 81 over 5 tests means that her total score over the 5 tests was 5*81 = 405.
The difference between those two scores, one over 4 tests and the other over 5 tests gives Kim's score over the 5th test.
405 - 312 = 87.
She scored 87 in the 5th test.
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