$A$ book seller allowed $10 \%$ discount on the printed price. He gets a $30 \%$ commission from the publisher. His profit percentage will be:

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

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

If the banker's discount on a certain sum in $2$ years at a certain rate is $Rs. 150$ and the simple interest on the same sum in $3$ years is $Rs. 240$,find the sum (in $Rs.$) and the rate of interest (in $\%$).

The marked price of an article is $Rs. 650$ and a customer pays $Rs. 585$ for it. What is the discount percentage (in $\%$)?

Ramesh marks his article at $Rs. 6000$ and after allowing a discount of $20 \%$, he still earns $60 \%$ profit. What is the cost price (in $Rs.$) of the article?