SOLUTION: after taking 7 quizzes, your average is 78 out of 100. what must your average score be on the next five quizzes to increase your average to 83?

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Question 307089: after taking 7 quizzes, your average is 78 out of 100. what must your average score be on the next five quizzes to increase your average to 83?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
after taking 7 quizzes, your average is 78 out of 100.
what must your average score be on the next five quizzes to increase your average to 83?
:
Let x = av score on the next 5 quizzes
:
We want the average for 7 + 5 = 12 quizzes
:
%287%2878%29+%2B+5x%29%2F12 = 83
%28546+%2B+5x%29%2F12 = 83
Multiply both sides by 12
546 + 5x = 12(83)
:
546 + 5x = 996
:
5x = 996 - 546
:
5x = 450
x = 450%2F4
x = 90 av required on the next 5 quizzes