Question

Your math test scores are 68, 78, 90, and 91. what is the lowest score that you can earn on the next test and still achieve an average of at least 85?

Answer 1

Let the unknown test score be x.

Average = 85


`(68 + 78 + 90 + 91 + x)/(5) = 85`


`(327 + x)/(5) = 85`

327 + x = 425

x = 98

Thus, the lowest score needed to be earned is 98.

Answer 2

98 is the lowest score that you can earn on the next test and still achieve an average of at least 85.

Explanation:

Math test scores are: 68, 78, 90, and 91

Average of the math test score = A = 85

Let the lowest score needed to achieve an average of 85 be x

Average =
`\frac{\text{Sum of terms}}{\text{Number of terms}}`

`A=(68+ 78+ 90+91+x)/(5)`

`85=(68+ 78+ 90+91+x)/(5)`

`68+ 78+ 90+91+x=425`

`x=425-(68+ 78+ 90+91)=98`

98 is the lowest score that you can earn on the next test and still achieve an average of at least 85.