Question

Tara wants her mean (average) quiz mark in class to be 90. Her marks in the first three quizzes were 92, 85 and 95. What marks should she get in the 4th quiz in order to have a mean (average) quiz mark of exactly 90?

Answer 1

Let x marks she should get in the 4th quiz.

(92+85+95+x)/4 = 90

92+85+95+x = 90×4

92+85+95+x = 360

272+x = 360

x = 360 - 272

x = 88

Hence, she should get 88 marks in the 4th quiz.