Three years ago, the population of a town was 50000.

Here,

$\mathrm{P}=$ Initial population $=50,000$

$\mathrm{R}_{1}=4 \%$

$\mathrm{R}_{2}=5 \%$

$\mathrm{R}_{3}=3 \%$

$\mathrm{n}=$ Number of years $=3$

$\therefore$ Population after three years $=\mathrm{P}\left(1+\frac{\mathrm{R}_{1}}{100}\right)\left(1+\frac{\mathrm{R}_{2}}{100}\right)\left(1+\frac{\mathrm{R}_{3}}{100}\right)$

$=50,000\left(1+\frac{4}{100}\right)\left(1+\frac{5}{100}\right)\left(1+\frac{3}{100}\right)$

$=50,000(1.04)(1.05)(1.03)$

$=56,238$

Hence, the population after three years is 56,238 .