SSC CHSL 5 Mar 2018 Shift 3 Paper

Principal amount = Rs. 2000
Amount after 2 years = Rs. 3645
Amount under compound interest = $\mathit{P}{\left(1+\frac{\mathit{R}}{100}\right)}^{\mathit{T}}$
⇒ $2000{\left(1+\frac{\mathit{r}}{100}\right)}^2=3645$
⇒ ${\left(1+\frac{\mathit{r}}{100}\right)}^2=\frac{3645}{2000}=1.8225$
Squaring both sides, ⇒ ${\left(1+\frac{\mathit{r}}{100}\right)}^4=3.32150625$ -----------(i)
∴ Sum after 4 years = $\mathit{P}{\left(1+\frac{\mathit{r}}{100}\right)}^4$
Substituting value from equation (i), we get :
= $2000\times 3.32150625=\mathit{R}\mathit{s}.6643.0125$