Question

The population of a town increases by 5 % annually . if its population at present is 1,85,220, then its popu- lation 3 years ago?

Answer 1

let population before three years be x. It increased 5% every year for three years. so,
[x * (105/100) * (105/100) * (105/100) ] = 1,85,220
Solve for x and you get x=1,60,000.
If you want you can check in reverse.