Question

The sum of three consecutive multiples of 9 is 108. The average of these multiples is

• A. 30
• B. 36
• C. 18
• D. 24

Answer 1

The correct option is B 36

If x is a multiple of 9, then next multiple is (x + 9)

The subsequent multiple of 9 will be (x + 9 + 9) = (x + 18)

So the three consecutive multiples of 9 are x, (x + 9) and (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, the first multiple of 9 is 27
The second multiple is 27 + 9 = 36
The third multiple is 27 + 18 = 45.
Average of these multiples = $\frac{27+36+45}{3}$
= 36