Question

Find the sum of the first $8$ terms of the geometric series if $a_1=2$ and $r=2$.

• A. $210$
• B. $310$
• C. $410$
• D. $510$

Answer 1

The correct option is D $510$

Given, $a_1=2,r=2$

$S_n=\frac{a_1(r^n-1)}{r-1}$
$S_8=\frac{2(2^8-1)}{2-1}$
$=\frac{2\left(255\right)}{1}$
$=510$