Question

Shelby will take a total of 6 tests. On the first 5 tests, her scores were: 80, 85, 73, 78, 90. If she wants a mean grade of 80, what does Shelby have to score on her 6th test?Group of answer choices84809074

Answer 1

74

Explanation:

Total number of tests = 6

The 5 test scores: 80, 85, 73, 78, 90

mean grade = 80

let the 6th test score = y

$\begin{gathered} \operatorname{mean}\text{ =}\frac{s\text{ um of al 6 scores}}{nu\text{mber of scores}} \\ \\ 80\text{ =}\frac{80+85+73+78+90+y}{6} \\ 80\text{ = }\frac{406\text{ + y}}{6} \end{gathered}$$\begin{gathered} 80(6)\text{ = 406 + y} \\ 480\text{ = 406 + y} \\ 480\text{ - 406 = y} \\ y\text{ = 74} \end{gathered}$

Shelby needs to score 74 on her 6th test