SOLUTION: Lucy has taken four tests In math and has an average of 85. What score does she have to get on her 5th test to have an average of 88?

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Question 987727: Lucy has taken four tests In math and has an average of 85. What score does she have to get on her 5th test to have an average of 88?
Found 2 solutions by macston, Edwin McCravy:
Answer by macston(5194) About Me  (Show Source):
You can put this solution on YOUR website!
.
Current sum of scores=4(85)=340
Sum needed to average 88 over 5 tests=5(88)=440
440-340=100
ANSWER: She must score 100 on the fifth test to have an 88 average.

Answer by Edwin McCravy(20059) About Me  (Show Source):
You can put this solution on YOUR website!
It's the same as if she had made exactly 85 on each of the first four tests.
Suppose she needs to make N on the 5th test to have an average of 88:

%2885%2B85%2B85%2B85%2BN%29%2F5%22%22=%22%2288

%28340%2BN%29%2F5%22%22=%22%2288

Multiply both sides by 5

340%2BN%22%22=%22%22440

N%22%22=%22%22100

She'll have to make a perfect score.

Edwin