SOLUTION: Your test grades are 72,76,90 and 90. What is the lowest grade you can earn on the last test and still have an average of at least 85?

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Question 712360: Your test grades are 72,76,90 and 90. What is the lowest grade you can earn on the last test and still have an average of at least 85?
Answer by Simnepi(216) About Me  (Show Source):
You can put this solution on YOUR website!
to achieve a mean score of 85 over 5 tests then the total score for those 5 tests must be 85*5 = 425
the total score so far, over 4 tests, is 72 + 76 + 90 + 90 = 328
so the difference between these two numbers is the score needed in the 5th and final test
425 - 328 = 98
so 98 marks are required.