Question

14.how many terms are there in the gp 5,20,80,320,.....20480?

Answer 1

7 terms are there in the GP. ..

hope it's help. ...

Answer 2

a=5 r=20/5=4
gp =ar^n-1
20480 =5*4^n-1
4096=4^n-1
4^6=4^n-1
6=n-1
n=7 terms