Question

the first term of a g. p is 4 and 4th term is 108. find the common ratio and the sum of four term.

Answer 1

this is example
If the 3rd term of GP is 12 and the 6th term is 96, then what is the sum of the 9th term?


ar^2=12 …(i)

ar^5=96 …(ii)

Dividing (ii) by (i)

r^3=8

Or, r=2

Sum of a gp is

S= a(r^n-1)/(r-1)

Therefore, S=1533

I hope this will help you