Management Aptitude Test Dec 2019 Paper

Let the principal be $\mathrm{P}$ and rate of interest be $\mathit{r}\%$ .
Then, principal (when difference between $\mathrm{Cl}$ and $\mathrm{SI}$ is for 2 yr) is given by $\mathit{P}=\frac{20\times {\left(100\right)}^2}{{\mathit{r}}^2}$ ...(i)
and principal (when difference between $\mathrm{Cl}$ and $\mathrm{SI}$ is for 3 yr) is given by $\mathit{P}=\frac{61\times {\left(100\right)}^3}{{\mathit{r}}^2\left(300+\mathit{r}\right)}$ ...(ii)
From Eqs. (i) and (ii),
$\frac{20\times {10}^4}{{\mathit{r}}^2}=\frac{61\times {10}^6}{{\mathit{r}}^2\left(300+\mathit{r}\right)}$
$\Rightarrow \mathit{r}=305-300=5\%$
Hence, from Eq. (i),
$\mathit{P}=\frac{20\times {10}^4}{25}=\mathit{₹}8000$