Question

Find the sum of the geometric sequence.

1/3 , 2/3 , 4/3 , 8/3 , 16/3

Answer 1

I believe the answer is 31/3

Answer 2

Sum of n terms = a1 * r^n - 1
---------------
r - 1

a1 = 1/3 and common ratio r = (2/3) / (1/3) = 2

so sum of 5 terms = (1/3) * (2*5 - 1) / 2-1 = 31/3


This is easily checked by just adding up the 5 terms