Average with Additional Item

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A student's average (arithmetic mean) test score on 4 tests is 68. What must be the student's score on a 5th test for the student's average score on the 5 tests to be 70?

Review: Average with Additional Item


Explanation

This question is about averages. Typically, average questions are made easier by working with the sums, using the twist on the average equation:



From the first 4 tests, we have



Using this equation again separately, if the fifth test gives an overall average of 70, then



The difference of the sums is , so that would have to be the fifth test score to meet the condition stated by the question. The correct answer is (E).


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