Question

The numbers 3, 5, 7, a, and b have an average of 15. What is the average of a and b?

Answer 1

The average of the 5 numbers is given to be

(3 + 5 + 7 + a + b)/5 = 15

Solve for a + b :

(15 + a + b)/5 = 15

15 + a + b = 75

a + b = 60

The average of a and b is then

(a + b)/2 = 60/2 = 30

Answer 2

3+5+7=15
therefore you don’t want to affect the average so your going to want your numbers to be equal length away from 15 so there are multiple answers one answer would be

a=14
b=16