SOLUTION: A student has earned scores of 87, 81, and 88 on the first 3 of 4 tests. If the student wants an average (arithmetic mean) of exactly 87, what score must she earn on the fourth tes

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Question 240584: A student has earned scores of 87, 81, and 88 on the first 3 of 4 tests. If the student wants an average (arithmetic mean) of exactly 87, what score must she earn on the fourth test?
A. 85
B. 86
C. 87
D. 92
E. 93
Answer by unlockmath(1688) About Me  (Show Source):
You can put this solution on YOUR website!
Hello,
Let's start by showing x for the 4th test. So now we can set up and equation.
(x+87+81+88)/4=87 OK, now let's multiply by 4 to remove the fraction.
x+87=81+88=348 Combine like terms
x+256=348 Subtract 256 from both sides to get:
x=92
There we go. Needs a score of 92 to get and average of 87.
Plug it in to see if it works.
RJ Toftness
www.math-unlock.com