Question

Jane has a average score of 73% on three quizzes. What must she score on the next quiz to have an average of 78%?

Answer 1

93

Explanation:

The average is calculated as

average =
`(sum)/(count)`

On 3 quizzes

`(sum)/(3)` = 73 ( multiply both sides by 3 )

sum = 219

On 4 quizzes, letting x be the score on fourth test

`(sum+x)/(4)` = 78 ( multiply both sides by 4 )

sum + x = 312 , that is

219 + x = 312 ( subtract 219 from both sides )

x = 93

She must score 93 on the next quiz