Question

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

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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

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