Question

Lena has scored 77 , 68 , 91 , 63 , and 68 on her previous five tests . What score does she need on her next test so that her average ( mean ) is 77 ?

Answer 1

Let us call x the score on Lena's next test, then we have

`(77+68+91+63+68+x)/(6)=77`

The above says that the average of six tests should be 77 and we just need to solve for x.

Simplifying the equation above gives

`(367+x)/(6)=77`

multiplying both sides by 6 gives

`367+x=462`

Finally, subtracting 367 from both sides gives

`\begin{gathered} x=462-367 \\ \boxed{x=95.} \end{gathered}`

Hence, Lena needs to score 95 in order that her average be 77.