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

add all the scores together and the divided by the number of scores there are

8 tests will be 8x91 = 728 

Then add on his latest test result 728+78 = 806 

Now divide by the number of tests (9) 806/9 = 89.55555555 
89.555%