math
posted by chris .
mikes average on the first four exams in econ 1A is 88. what must he earn on the next exam to raise his overall average to 90

math 
MattsRiceBowl
I would start by figuring out how many points he has total so far.
88 average * 4 tests = 352 points.
So then the question is, 352 + how many points ALL divided by 5 tests = 90?
(352+x)/5 = 90
352+x = 450
x = 98.
Now, let's check our work.
352 + 98 = 450
450 / 5 = 90
OR...
We could use basic logic. We could say "Mike needs 2 more points in each test so far to get him to a 90 in each test. There were four tests. 4 test * 2 points a test is 8 points. So on this exam, he needs 90 points, plus 8 points to make up for the others. So he needs a 98."
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