Question

Susie scored 85, 84,and 78 on three of the four math tests. if her average score for the four tests was 86. what was her score on the fourth test?

Answer 1

(85 + 84 + 78 + x) / 4 = 86
(247 + x) / 4 = 86
247 + x = 86 * 4
247 + x = 344
x = 344 - 247
x = 97 <=== her score was 97

Answer 2

Susie's average score was 86 so if you take 86 x 4 it would equal 344 which is her total points scored on the four tests. Take the total 344 - 85 = 259; then 259  - 84 = 175; then 175 - 78 = 97. The 97 is Susie's fourth test score because when you combine the four individual test scores you get 344. Take 344 and divide it by 4 and you will 86 which was her average score. Fourth test is 97.