Apopulation that doubles in size every 14 years has a growth rate of?

Let's say there is 50 people. In 40 years the population then is 100.
50/14 = 3.6 -- Since you can't exactly split a single person up, you'd have to round up to 4, and some years being 3. Since it is a rate however, 3.6 would be technically okay.

Number wise, the rate is 3-4 people every year.
Percentage wise, the rate is 7.2% growth rate every year.

Simply take 3.6/50 = 0.072
0.072 x 100 = 7.2%
:D