SOLUTION: how do you find the missing number to get a certain average with 5 numbers.

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Question 486077: how do you find the missing number to get a certain average with 5 numbers.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
how do you find the missing number to get a certain average with 5 numbers.
:
Let x = the missing grade
An example the 5 grades: 84, 88, 79, 92, x
The certain average is 85
:
The equation
%2884%2B88%2B79%2B92%2Bx%29%2F5 = 85
which is:
%28343%2Bx%29%2F5 = 85
multiply both sides by 5,
343 + x = 5*85
343 + x = 425
subtract 343 from both sides
x = 425 - 343
x = 82 would be the missing grade to obtain an 85 average