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