Question

Question #bfd15

Answer 1

`n=12`

Explanation:

The geometric sequence is `2^1 , 2^2 ,2^3 ........, 2^n`

Here the first term and common ratio are `a=2 and r=2`

We know sum `s_n= a*(r^n-1)/(r-1) :. 2*(2^n-1)/(2-1)=8190` or

`2^n-1=8190/2=4095 or 2^n=4096 or 2^n= 2^12 :. n=12` [Ans]