Ella's test grades in her history class are 89, 94, 82, 84, and 98. What score must Ella make on her next test to have a mean
test score of 90?
needed on the next test

93

Step-by-step explanation:

set the test score she needs as x.

the mean is 90, so 89+94+82+84+98+x=90*6=540. solving this, we get x=93

93

Step-by-step explanation:

To calculate mean you sum the score of all of the test scores and divide that by the number of tests. We can use this formula to work backwards from the mean 90.

If the mean of 6 tests is 90 that means the combined total of all the scores is equal to 90 * 6 which is 540. Right now the total of Ella's 5 test grades is 447.

If you subtract 447 from 540, the result will be the test score needed to get a mean of 90.

540 - 447 = 93