Question

Simon must maintain an average grade of 80% or better in his math class to be eligible to play sports.His math grade so far are 80%, 84%, 76%, 77% at this point his grades make him ineligible to play.What is the lowest he can score on the next grade to bring his average score up to 80%. Wright and inequality to represent the average of the five grades as greater than or equal to 80%. Use the Inequality To prove what his lowest score could be on the fifth test.

Answer 1

Let x be the percentage score he got in fifth test,

According to the question,

His score in first, second, third and fourth test are 80%, 84%, 76% and 77% respectively,

Thus, the average of his total score in the five test,

=
`(80+84+76+77+x)/(5)`

But, Again according to the question,

The average of the five grades as greater than or equal to 80%

That is,

`(80+84+76+77+x)/(5)\geq 80`

⇒
`(317+x)/(5)\geq 80`

⇒
`317 + x \geq 400`

⇒
`x\geq 83`

Thus, the least score he can get in the fifth test is 83.