Find the sum of first 8 multiples of 3.

Given: First 8 multiples of 3.

To do: To find the sum of first 8 multiples of 3.

First 8 multiples of 3 are

3, 6, 9, 12, 15, 18, 21, 24

The above sequence is an A.P.

Whose first term, $a=3$, common difference, $d = 3$ and last term $l=24$

As known sum first n terms of an A.P.$=\frac{n}{2}( a+l)$

                                                                $=\frac{8}{2}( 3+24)$

                                                                 $=4( 27)$

                                                                 $=108$

Therefore sum of first 8 multiples of 3 is 108.