The third term of a G. P. is 12 and 6th term is 96, then find the sum of nine terms of the G. P.

Answer 1

3rd term is ar^2=12 and 6th term is ar^5=96 To find r we divide 6th term by 3rd term. So r =2. Then substitute in 3rd term and so the 1st term(a) =3. So GP sum of 9 terms is S9=a(r^n-1)/r-1. Substituting we have S9=3(2^9-1)/2-1. So the answer is 1533