AVERAGE PROBLEM
Sam has an average of 70 on 4 different tests. If the lowest score is dropped, her average rises to 90. What is the lowest score?
SOLUTION:
Total for 4 tests is 70 x 4 = 280.
Total for 3 tests is 90 x 3 = 270.
Therefore, the score on the 4th test must have been 10.
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