Posted by **Anonymous** on Wednesday, July 18, 2012 at 1:18am.

The population of the world in 1987 was 5 billion and the annual growth rate was

estimated at 2 percent per year. Assuming that the world population follows an

exponential growth model, find the projected world population in 2015.

- maths -
**MathMate**, Wednesday, July 18, 2012 at 9:13am
Assume formula

Population in billions at time t (counting from 1987) as

P(t)=Ae^(kt)

where A and k are constants.

At t=0 (1987),

P(0)=Ae^(0)=A=5

the formula becomes:

P(t)=5e^(kt)

P(1)=5*1.02=5e^(kt) [t=1]

=>

e^(k)=1.02 [t=1]

Take log both sides

k=log(1.02) [natural log]

So

P(t)=5e^(t*log(1.02))

where log(1.02)=0.0198 approx.

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