The sum of an infiinte series exists when the ratio is in the interval (-1,1)
Here the ratio is 1/3, then the sum exists.
The formula for this sum is A / (1 -r); where A is the first term and r is the ratio
Then, the sum is [1/3] / [1 -1/3] = [1/3] / [2/3] = 1/2
Answer: 1/2
