In chemistry class Andrew has earned scores of 64 69 and 73 on three tests he must maintain an average of 72

You haven't told me what the question is. But I put the mouse

to my forehead, closed my eyes, took a deep breath, and I could

see it shimmering in my mind's eye. It was quite fuzzy, but I think

the question is

"What score does Andrew need on the next test

in order to raise his average to 72%?"

The whole experience drew an incredible amount of energy

out of me, and the mouse is a total wreck. So we'll just go ahead

and answer that one. I hope it's the correct question.

The average score on 4 tests is

(1/4) (the sum of all the scores).

In order for Andrew to have a 72% average on 4 tests,

the sum of the 4 scores must be

(4) x (72%) = 288%.

Out of that total that he needs, he already has

(64% + 69% + 73%) = 206%

on the first three tests.

So in order to average 72% for all 4 tests,

he'll need to score

(288% - 206%) = 82%

on the fourth one.