Population increase problem?

Question

A city of 250,000 people is growing at a rate of 1.3% per year. Estimate the population of the city 30 years from now.

1. S(31) = 250,000(1.3)^(31-1)
2. S(30) = 250,000(1.3)^(30-1)

Which set-up is correct?

Answer 1

now = 0
s(30) = 250,000(1.013)^30

1.3% = 0.013, so growth factor is 1 + 0.013 = 1.013