Find the doubling time for a city whose population is growing by 25% per year.

Answer 1

2A= Ae^.25t, divide by A, then take natural logs of both sides

ln2 = .25t divide by .25

t = ln2/.25 = about 2.77 years

if the growth is continuous, compounded continously like interest

start with 100, end of 1 year is 125, end of 2 years is 1/4 more or 156.25. end of 3 years add another 1/4 to get 156.25 + 39.0625 = 194.3125 a little over 3 years doubling time, for non-continuous growth, compounded annually.