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

Question 200311: 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?
Found 2 solutions by RAY100, nerdybill:
Answer by RAY100(1637) (Show Source): You can put this solution on YOUR website!
87 + 81 + 88 +x = total score = 256 +x
.
avg score = 87 = (256+x) / 4
.
256 +x = 348
.
x= 92
.
Check,,,( 87+81+88+92 ) /4 = 87
Answer by nerdybill(7384) (Show Source): You can put this solution on YOUR website!
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?
.
Let x = score on fourth test
then
(x+87+81+88)/4 = 87
(x+256)/4 = 87
Multiplying both sides by 4:
(x+256) = 87*4
(x+256) = 348
x = 348-256
x = 92 (score for fourth test)

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