Question

mary has scored 78 , 60 , 82 , 94 , and 88 on her previous fice tests . What score does she need on her next test so that her average ( mean ) is 80 ?

Answer 1

Mary has scored 78, 60, 82, 94, and 88 on her previous fice tests.

What score does she need on her next test so that her average (mean) is 80?

Let x be the next test score

Recall that the mean is given by

`mean=\frac{\text{sum of test scores}}{total\text{ numbers of tests}}`

We have the following information,

mean = 80

sum of test scores = 78 + 60 + 82 + 94 + 88 + x = 402 + x

total number of tests = 6

So, let us substitute these values into the above formula

`\begin{gathered} mean=\frac{\text{sum of test scores}}{total\text{ numbers of tests}} \\ 80=(402+x)/(6) \\ 6*80=402+x \\ 480=402+x \\ 480-402=x \\ 78=x \\ x=78 \end{gathered}`

Therefore, Mary need to score 78 on her next test so that her mean is 80