SOLUTION: a boy received the following marks in algebra: 72,90,70,80. what must be his fifth mark if his average for the five tests is to be 80%?

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Question 819877: a boy received the following marks in algebra: 72,90,70,80. what must be his fifth mark if his average for the five tests is to be 80%?
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 
Hi,
a boy received the following marks in algebra: 72,90,70,80. Total 312
what must be his fifth mark green%28X%29 if his average for the five tests is to be 80%?
%28312+%2B+x%29%2F5+=+80+
312 + x = 400
x = 88, what his fifth mark must be to average 80%