You scored 88,92, and 87 on three tests. Write and solve an equation to find the score you need on the fourth test so that your mean test score is 90.

Question

You scored 88,92, and 87 on three tests. Write and solve an equation to find the score you need on the fourth test so that your mean test score is 90.

Answer 1

(88+92+87)/3 = 267/3= 89 average for the 1st 3 tests

you need 90 for an A

take the weighted average of 89 and one more test grade = x

89 has weight 3, x has weight 1, 90 has weight 3+1=4

3(89)+1(x) = 4(90)

267 + x =360

x = 360-267 = 93 for the 4th test to get a 90 mean average grade