Question:
The population of a town increases at the rate of 40 per thousand annually. If the present population be 175760, what was the population three years ago.
Solution:
Population after three years $=\mathrm{P}\left(1+\frac{\mathrm{R}}{100}\right)^{3}$
$175,760=\mathrm{P}\left(1+\frac{40}{1000}\right)^{3}$
$175,760=\mathrm{P}(1.04)^{3}$
$\mathrm{P}=\frac{175,760}{1.124864}$
$=156,250$
Thus, the population three years ago was 156,250 .