The true discount on a bill of $Rs. 2550$ due after $3$ months is $Rs. 50$. Find the banker's discount (in $Rs.$).

$A$ bill is discounted at $5 \%$ per annum. If banker's discount be allowed, at what rate of interest must the proceeds be invested, so that nothing is lost? (in $\%$)

What was the rate of discount if a computer with a marked price of $Rs. 30,000$ was sold for $Rs. 28,000$? (in $\%$)

If $21 \%$ of an electricity bill is discounted,$Rs. 1817$ is still to be paid. How much was the original bill amount? (in $Rs.$)

The true discount on a certain bill due for nine months at $4 \%$ simple interest is $Rs.\, 150$. Find the amount of the bill (in $Rs.$).

The difference between the simple interest and the true discount on a certain sum of money for $2$ years at $15 \%$ per annum at simple interest is $Rs. 45$. Find the sum (in $Rs.$).