A student's scores on 5 tests are 90, 75, 90, 80, 90. What score is needed on the next test for an average of 80 over all 6 tests?
Answer and explanation
Correct answer: C. 55
- Step 1: The total needed is 80 x 6 = 480.
- Step 2: The scores so far add up to 425, so the next test needs 480 - 425 = 55.
Answer
55.
Why not the others: Scoring 80 only matches the target if the earlier average is already 80; -25 uses only 5 tests in the total.
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