The population of a town increases at the rate of 50 per thousand.
Question:

The population of a town increases at the rate of 50 per thousand. Its population after 2 years will be 22050. Find its present population.

Solution:

Population after two years $=\mathrm{P}\left(1+\frac{\mathrm{R}}{100}\right)^{\mathrm{n}}$

$22,050=\mathrm{P}\left(1+\frac{50}{1000}\right)^{2}$

$22,050=\mathrm{P}(1.05)^{2}$

$\mathrm{P}=\frac{22,050}{1.1025}$

$=20,000$

Thus, the population two years ago was 20,000 .