The present worth of a sum due after a certain time is $Rs. 1024$ and the banker's gain is $Rs. 36$. The true discount is (in $Rs.$):

When a discount of $20 \%$ is given on a sweater,the profit is $28 \% .$ If the discount is $14 \%,$ then the profit is (in $\%$)

$Rs. 21$ is the true discount on $Rs. 371$ for a certain time at a certain rate of interest. If the rate of interest is kept the same,the true discount on the same sum for double that time will be (in $Rs.$)

If the selling price is $Rs. 1680$ after getting a discount of $16 \%$ what was the marked price? (in $Rs.$)

$A$ bill which is due at the end of $4 \text{ years}$ is now worth $Rs. 575$,but if it is due in $2 \frac{1}{2} \text{ years}$,it would now be worth $Rs. 620$. The sum of the bill is (in $Rs.$)

If the true discount on $Rs. 161$ due for $2$ years and $6$ months is $Rs. 21$, then find the rate of interest (in $\%$).