The population of a small town decreased from 18,000 to 15,000 due to the breakout of an epidemic. What is the percentage decrease in the population?

Initial population = 18,000

Decreased population = 15,000

Decrease in population = 18,000 – 15,000 = 3,000

∴ Percentage decrease in population

$=\left(\frac{\mathrm{Decrease} \mathrm{in} \mathrm{population}}{\mathrm{Initial} \mathrm{population}}\right)\times 100$

$=\left(\frac{3,000}{18,000}\right)\times 100$

$=16.67\%$

Hence, the percentage decrease in population is 16.67%.