SOLUTION: Susan Jacobson has grades of 76 and 81 on her first two algebra tests. If she wants an average of at least 80 after her third test, what score must she make on that test?

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Question 722812: Susan Jacobson has grades of 76 and 81 on her first two algebra tests. If she wants an average of at least 80 after her third test, what score must she make on that test?
Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
x= grade for the third test.
For the average after the third test to be 80, the sum of all 3 test grades divided by 3 must be 80.
average=%2876%2B81%2Bx%29%2F3=80
Multiplying both sides of the equal sign times 3, we get
76%2B81%2Bx=80%2A3 --> 157%2Bx=240 --> x=240-57 --> highlight%28x=83%29
That is probably the expected answer.

However, in real life, thanks to rounding, Susan could get away with an 82, because
76%2B81%2B82%29%2F3=235%2F3=79%262%2F3 and that rounds up to 80.