The population of a town is 4.2 × 106. If the population increases by 75 per 1000 per annum, then what will be the population after 2 years ?

Answer: Option B

Percentage annual increase :
$$\begin{array}{rl}& =\left(\frac{75}{1000}\times 100\right)\%\\ & =7\frac{1}{2}\%\\ & =\frac{15}{2}\%\end{array}$$
Population after 2 years :
$$\begin{array}{rl}& =4200000{\left(1+\frac{15}{2\times 100}\right)}^2\\ & =\left(4200000\times \frac{43}{40}\times \frac{43}{40}\right)\\ & =4853625\end{array}$$