Question

Cory's average score after 8 tests is 91%. If he gets a 78% on his 9th test what will his new average be?

Answer 1

You should be able to multiply 91 by 8 to get the sum of the first 8 tests, then add the score on the 9th test. Then to get the average of the sum of the 9 tests you need to divide it by 9.
((91*8)+78)/9=89.555555555555.... So, 90%