The population of a village has increased annually at the rate of 25%. If at the end of 3 years it is 10000, the population in the beginning of the first year was :

Answer: Option A

25% = $$\frac{1}{4}$$
$$\begin{array}{c}\text{Initial }\text{Final}\text{hfill}\\ 45\text{hfill}\\ 45\text{hfill}\\ 45\text{hfill}\\ \overline{64125}\text{hfill}\end{array}$$

⇒ 125 units = 10000
⇒ 1 unit       = 80
⇒ 64 units = 5120
⇒ Population at the beginning of 1^st year = 5120