Question

The population of a city increases $15\%$ annually. If the present population is $20,700$. find the population a year ago.

Answer 1

Let the last year population be $x$

Percentage Increase annually $=15\%$

Then,the present year population $=x+15\%$ of $x=x+0.15x=1.15x$

It is given that the present population of the city is $20700$.

$\therefore 20700=1.15x$

$\Rightarrow x=\frac{20700}{1.15}$

$\Rightarrow x=18000$

Hence, the population one year ago was $18000$.