SOLUTION: if the scores for three tests are 96, 98, and 86, what must the scores on a fourth test be to make the average 90

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Question 1178853: if the scores for three tests are 96, 98, and 86, what must the scores on a fourth test be to make the average 90
Found 2 solutions by ankor@dixie-net.com, greenestamps:
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
f the scores for three tests are 96, 98, and 86,
what must the scores on a fourth test be to make the average 90
:
let x = the score of the 4th test
:
%28%28x+%2B+96+%2B+98+%2B+86%29%29%2F4 = 90
%28%28x+%2B+280%29%29%2F4 = 90
Multiply both sides by 4
x + 280 = 360
x = 360 - 280
x = 80 score will give an average of 90
:
You can confirm this, add up the 4 scores and divide by 4

Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


Here is an alternative method for solving this kind of average problem if the numbers are all close together. I think it's easier because the numbers you need to work with are smaller....

Compared to the desired average of 90...
96 is +6
98 is +8
86 is -4

Together those three scores are 6+8-4=+10.

So the score on the fourth test must be -10.

ANSWER: 90-10 = 80