RRB Paramedical Staff Nurse Model Paper 5

The Simple interest on certain amount is 500 and the compound interest is Rs 520 . it means the interest on interest for the first year $=520-500=20$
So the rate of interest $=\frac{20}{250}\times 100=8\%$
Principle for the first year was Rs.3125
$\frac{\mathit{P}\times 1\times 8}{100}=250$
$\mathit{P}=3125$
$\frac{\mathit{P}\times \mathit{k}\times \mathit{k}}{100}=\mathit{S}\mathit{I}$
Now, $\frac{3125\times {\mathit{k}}^2}{100}=950$
${\mathit{k}}^2=30.4$
$\mathit{k}=5.513$