Question

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

• A. 56
• B. 26
• C. 36
• D. 46

Answer 1

The correct option is C 36

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