SOLUTION: three exam scores of 70, 60, and 40 what score would you need on the fourth exam to give an average of 72.0

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Question 15154: three exam scores of 70, 60, and 40 what score would you need on the fourth exam to give an average of 72.0
Answer by pramboggle(1) About Me  (Show Source):
You can put this solution on YOUR website!
To find the mean (or average) of a problem you add together the numbers then divide by however many numbers there are. In this case you only have 3 of the 4 numbers you need. Use x for the fourth.
%28%2870%2B60%2B40%2Bx%29%2F%284%29%29=+72
Then yoy want to solve for x. Make the 72 a 72%2F1.
%28%2870%2B60%2B40%2Bx%29%2F%284%29%29=+%2872%2F1%29 Then cross multiply.
%28%28170%2Bx%29%2F4%29=%2872%2F1%29
1%28170%2Bx%29=%284%29%2872%29
170%2Bx=288
x=118
If you want to check your answer you go back and plug in 118 for x.
%2870%2B60%2B40%2B118%29%2F4=72
It works! So 118 is your answer.