Question

In a GP the sum of first n terms is 4095 common ratio is 2 and the last term is 2048 find n ​

Answer 1

Correct option is C = 4

Since, a=3,a

r−1

=3072 and s

n

=

1−r

a(1−r

n

)

4095=

1−r

a+ar

n−1

r

⇒4095=

1−r

3−3072r

⇒4095=

1−r

3(1−1024r)

⇒1365=

1−r

1−1024r

⇒1365(1−r)=1−1024r

⇒1365−1365r=1−1024r

⇒341r=1364

⇒r=4

Then common ratio of GP is 4