Question

The mean of Holly's first six math quiz scores was 75%. After taking the seventh quiz, her mean score rose to 77%. What was Holly's score on the seventh math quiz?

Answer 1

Let x represent Holly's score on 7th math quiz.

We have been given that the mean of Holly's first six math quiz scores was 75%. This means that the average on 1st 6 math quizzes is 75.

To find the total scores on 1st 6 math quizzes, we will multiply 75 by 6 that is
`75* 6 =450`.

We will use average formula to find test scores on 7th math quiz.

`\text{Average of 7 math quizzes}=\frac{\text{Sum of scores on 7 math quizzes}}{\text{7 quizzes}}`

`77=(x+450)/(7)`

Let us solve for x.

`77\cdot 7=(x+450)/(7)\cdot 7`

`539=x+450`

`x+450=539`

`x+450-450=539-450`

`x=89`

Therefore, Molly's score on the 7th math quiz was 89.