Question

If the sum of three consecutive multiples of 9 is 108, then the average of those multiples is ___ .

Answer 1

If x is a multiple of 9, then next multiple is x + 9.

The next to this is x + 9 + 9 = x + 18.

So three consecutive multiples of 9 are x, x + 9, x + 18

As per the question

x + (x + 9) + (x + 18) = 108

3x + 27 = 108

x = $\frac{108-27}{3}$ = $\frac{81}{3}$ = 27
So, first multiple is 27
Second multiple is 27 + 9 = 36
Third multiple is 27 + 18 = 45.
Average of multiples = $\frac{27+36+45}{3}=36$