<PRE><B>Question 307089</B>
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
:
{{{(7(78) + 5x)/12}}} = 83
{{{(546 + 5x)/12}}} = 83
Multiply both sides by 12
546 + 5x = 12(83)
:
546 + 5x = 996
:
5x = 996 - 546
:
5x = 450
x = {{{450/4}}}
x = 90 av required on the next 5 quizzes</PRE>