The population of a town increases by 10% annually.
Question:

The population of a town increases by 10% annually. If the present population is 22000, find its population a year ago.

Solution:

Let the population of the town one year ago $=x$

Now, it is given that population of the town increases by $10 \%$ annually.

Present population $=x+10 \%$ of $x$

$=x+\frac{10}{100} \times x$

$=x+\frac{x}{10}$

$=\frac{11 x}{10}$

But present population of the town $=22000$

So, $\frac{11 x}{10}=22000$

$\Rightarrow 11 x=220000$

$\Rightarrow x=\frac{220000}{11}$

$\Rightarrow x=20000$

So, population of the town 1 year ago $=20000$