Question

Pretend the world's population in 1989 was 5 billion and that the projection for 2017 is 7.5 billion.

What annual rate of growth is assumed in this prediction?

Answer 1

Assuming we take the growth to be exponential , ...

5 e^(28r) = 7.5

e^(28r) = 1.5
ln both sides

ln (e^(28r)) = ln1.5
28r = ln 1.5
r = .0145

the rate is 1.45%

check:
5 e^(28*.0145)
= 7.5