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?
.
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)