My favorite thing to do in my pastimes in calculate what I can get on a final test to keep an average.
First, we have to find out what the total of the 5 tests was. This is done by multiplying the average score by 5 (because in calculating the mean/average, we would originally divided all the scores added up by the number of tests):
88*5 = 440
Then we have to do the following to find the average score (which we know already:
90= (440+x)/6
540=440+x
x=540-440
=100
Her score on the sixth test was 100
