Question

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

• A. 22
• B. 28
• C. 36
• D. 44

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 and x + 18.
Given that: the sum of three consecutive multiples of 9 = 108
$\Rightarrow$x + (x + 9) + (x +18) = 108
$\Rightarrow$3x + 27 = 108
$\Rightarrow$x =$\frac{108-27}{3}$
x = $\frac{81}{3}$ = 27
So, the first multiple is 27,
Second multiple is 27 + 9 = 36 and
Third multple is 27 + 18 = 45.

$\Rightarrow$ Average of three consecutive multiples of 9 = $\frac{27+36+45}{3}$= 36.