Question

If the annual decrease in the population of a town by $5\%$ and the present population be $68590$, what was the population three years ago?

• A. $80000$
• B. $60000$
• C. $86000$
• D. $65000$

Answer 1

The correct option is A $80000$

Present population, $P=68590$

Let $R=5$%

The population three years ago

= $=\frac{P}{{(1-\frac{R}{100})}^3}=\frac{68590}{{(1-\frac{5}{100})}^3}=\frac{68590}{{\left(\frac{19}{20}\right)}^3}=\frac{68590\times 20\times 20\times 20}{19\times 19\times 19}=\frac{548720000}{6859}=80,000$