Question

If a population consists of ten thousand individuals at time t=0 (P0), and the annual growth rate (excess of births over deaths) is 3% (GR), what will the population be after 1, 15, and a 100 years (n)? Calculate the "doubling time" for this growth rate. Given this growth rate, how long would it take for this population of a hundred thousand individuals to reach 1.92 million? one equation that may be useful is:

Pt=Po * (1+ {GR/100})n

Additionally, using the current world population from the census website, calculate world population in 2100 with growth rates of 2.3% and 0.5% why is this important?

Answer 1

The first part of the question has been answered before. See:
http://www.jiskha.com/display.cgi?id=1254881441


For the second part of the question, it is essentially the same idea. By using the formula
P(2100)=P(2009)*(1+r)^(2100-2009)
where
P(t) = projected population in year t
r = rate of growth, for example, 0.023 or 0.005

If you need more help, post any time.

Answer 2

Your equation should be
Pt=Po * (1+ {GR/100})^n
The n is an exponent.

Why don't you just apply the formula?

After 100 years,
Pt/Po = (1.03)^100 = 19.2

Note that ratio also equals
1.92 million/100,000

The population doubling time is about 24 years. There is a handy approximate rule of thumb that says
(growth rate, %)*(doubling time, years) = 72

The exact answer is
log2/(log 1.03) = 23.45 years