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 $75\times 6 =450$.

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

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

$77=\frac{x+450}{7}$

Let us solve for x.

$77\cdot 7=\frac{x+450}{7}\cdot 7$

$539=x+450$

$x+450=539$

$x+450-450=539-450$

$x=89$

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