Question

Find the sum of first eight multiples of three.

Answer 1

Solution:-

First eight multiple of 3: $3,6,9,.......,24$

First term,$\left(a\right)=3$

Common difference, $\left(d\right)=3$

No. of terms, $\left(n\right)=8$

As we know that, sum of n terms of an A.P.-

$S_n=\frac{n}{2}(a+l)$

$S_8=\frac{8}{2}(3+24)$

$S_8=4\times 27=108$

Hence, sum of first eight multiples of three is 108.