Question

Ryan scored 87, 93, 96, and 89 on her first four history quizzes. What score does Ryan need to get on her fifth quiz to have an average of exactly 91 on her history quizzes?

Answer 1

Answer: For Ryan to get an average of exactly 91, she needs to get a 90 on her fifth quiz.

Step-by-step explanation:

You can find the average of a set of numbers by adding them together and dividing the sum by the amount of numbers added.

Ryan has five total quizzes. Only four of them are known, so we can represent her fifth quiz as X.

$\frac{87 + 93 + 96 + 89 + x}{5}$, dividing the five quizzes' sum by 5

She wants the average to be exactly 91, so you can set the expression equal to 91 and solve:

$\frac{365 + x}{5} = 91\\\\365 + x = 455\\\\x = 90$

For Ryan to get an average of exactly 91, she needs to get a 90 on her fifth quiz.