Question

The sum of first $8$ terms of the series $3,6,12,24,\dots$ is

• A. $452$
• B. $541$
• C. $689$
• D. $765$

Answer 1

The correct option is D $765$

Clearly, the given series in G.P.
Here $a=3,r=2>1$ and $n=8$
$S_n=\frac{a(r^n-1)}{(r-1)}$
$S_8=\frac{3\times (2^8-1)}{(2-1)}=3\times (256-1)=765$