Question

How to find the common ratio of a geometric series? With the first and last term given

Answer 1

I am trying to solve this: What is the sum of a 6-term geometric series if the first term is 21 and the last term is 352,947 but I don't know how to find its common ratio, help?

Answer 2

s = a1 / ( r-1) for an infinite GP


352,947 = 21 / ( r-1 )

(r-1 ) = 352947/21

r = 16807+1 = 16808
might be possible i m wrong but this logic help u a lot

Answer 3

use the formula :
Sn = a1(r^n - 1)/(r - 1)

Answer 4

Thank you, I got it now :)