Question

The sum of first 10 terms of the G.P 3, 6, 12, 24 .......... is

__.

Answer 1

a = 3

r = 2

Sum of n terms $S_n=\frac{a(r^n-1)}{r-1}$

$S_{10}=\frac{a(r^{10}-1)}{r-1}$

$=\frac{3(2^{10}-1)}{2-1}$

$=(1024-1)\times 3$

$=1023\times 3$

= 3069