If the population kept on growing at 5 percent per annum then

1) after 2 years the current population ie., 4,85,200 will increase to

4,85,200*(105/100)*(105/100) = 5,34,933.

2) Before 2 years let the population be X then it had to grow at 5 percent per annum to reach 4,85,200. So

X*(105/100)*(105/100)=4,85,200

Rearranging gives the population equal to 4,40,091.