The average of averages is found by getting the sum of both groups of numbers and dividing by the count of numbers.

Calculate the sum of the first group of numbers S1:

Average = S1 / n1

18 = S1 / 20

S1 = 20 * 18

S1 =360

Calculate the sum of the second group of numbers S2:

Average = S2 / n2

20 = S2 / 18

S2 = 18 * 20

S2 =360

Our average of averages is found by the following:

A = (S1 + S2)/(n1 + n2)

A = (360 + 360)/(20 + 18)

A = 720/38

**A = 18.947**