Peter's average (arithmetic mean) test score on 4 tests is 78. What must be the student's score on a 5th test for the Peter's average score on the 5 tests to be 80?
Choose the correct choice from the following answers
A) 80	B) 82	C) 84	D) 86	E) 88
E. 88   Peter must score at least an 80 for sure. If he scores an 8, then he will need to score 2 pots for each of the 4 other tests tomake upthe difference. They each were at 78 (at least the average is, but this is a small point and doesn't matter to the answer). So 4 tests that were each 2 points short of the 80 average that is desired means the next test must be 8 points higher than the desired average, so  80+8= 
<gadget id="calculator"> 80+8</gadget>
<output>88</output>
88.
<result>E</result>
Peter's average (arithmetic mean) test score on 4 tests is 78. What must be the student's score on a 5th test for the Peter's average score on the 5 tests to be 80?