The average of first five multiples of 3 is:

Answer: Option A

First five multiples of three are:
3, 6, 9, 12, 15.
$$\begin{array}{rl}& \text{Average}=\frac{3+6+9+12+15}{5}\\ & =\frac{45}{5}\\ & =9\end{array}$$

Alternatively,
Average = $$\frac{3+15}{2}=9$$