Question

Dwayne had a test average of 85.2 last semester. His first four test grades were 81,87 and 93. use the formula to find his score on the fifth test

Answer 1

Given:

Average of test is 85.2

First four test grade is : 81, 87, 79, 93

let fifth test grade is "x"

so average is:

`A\mathrm{}V\mathrm{}=(x_1+x_2+x_3+x_4+x_5)/(5)`
`\begin{gathered} 85.2=(81+87+79+93+x)/(5) \\ 5*85.2=81+87+79+93+x \\ 426=340+x \\ x=426-340 \\ x=86 \end{gathered}`

So the fifth test grades is 86.