Find the mean of first five multiples of 3.

First five multiples of 3 are 3, 6, 9, 12, 15.

$\therefore$ Mean $=\frac{\text { Sum of numbers }}{\text { Total numbers }}$

$=\frac{3+6+9+12+15}{5}=\frac{45}{5}$

= 9

Mean = 9