Question

Juan received scores of 82, 76, 93, and 80 on his first four chemistry tests of the year. His goal is to have an 86 average in chemistry for his first five tests. What score must he earn on the next test to achieve an average of exactly 86?

Answer 1

Answer:

99 marks

Step-by-step explanation:

Given:

Juan received scores of 82, 76, 93, and 80 on his first four chemistry tests.

His goal is to have an 86 average in chemistry for his first five tests.

Question asked:

What score must he earn on the next test to achieve an average of exactly 86?

Solution:

Let score he must earn on the fifth test = $x$

As we know:

Scores in five test = 82, 76, 93, 80, $x$

Total number of test = 5

We can find the score of fifth test, he must earn to achieve an average of exactly 86 by using this formula:

$Average =\frac{Sum\ of\ all\ observations}{Total\ observation}$

$86=\frac{82+76+93+80+x}{5}\\\\ 86=\frac{331+x}{5}$

By cross multiplication

$331+x=86\times5\\331+x=430$

Subtracting both sides by 331

$x=99$

Therefore, he must earn 99 marks to achieve an average of exactly 86 for his first five tests in chemistry.