Question

So far, a student has earned the following scores on four 100-point tests this grading period: 65, 73, 81, and 82. What score must the student earn on the fifth and last 100-point test of the grading period to earn an average test grade of 80 for the five tests?

Answer 1

99

Explanation:

Given:

A student has earned the following scores on four 100-point tests

65 73 81 82

Average grade of total five test = 80

Question asked:

What score must the student earn on the fifth and last 100-point test of the grading period to earn an average test grade of 80 for the five tests ?

Solution:

Let score earned in fifth test =
`x`

By using average formula:

Now, according to the question

Average grade of total five test = 80

Sum of all observation by tatal num. of observation = 80

`(65 + 73 + 81 + 82 + x)/(5)` =
`80`

`(301 + x)/(5) = 80\\`

Multiplying both side by 5

`301 + x = 400`

Subtracting both side by 301

`x = 99`

Therefore, he must score 99 to earn an average test grade of 80 for the five tests.