The third term of a geometric progression of positive terms is 18 and the fifth term is 162

Question

Find the common ration and the first term?

Write an expression for the Nth term of the progression?

Find the sum of the first 8 terms of the progression??

Answer 1

r^2 = 162/18 = 9

Now you can find the 1st term, and then

S8 = a(r^8-1)/(r-1)