After giving a discount of $20 \%$ on an article,a shopkeeper gains $20 \%$. What is the percentage mark-up?

$A$ dealer marks a washing machine for $Rs.\, 7500$ and allows a discount of $6 \%$ on it. Find its selling price in $Rs.$

If the simple interest on $Rs. 2000$ at $5\%$ $p.a.$ is equal to the true discount on $Rs. 2500$ for the same time and at the same rate,the time is (in $years$)

$A$ photographer allows a discount of $10 \%$ on the advertised price of a camera. The price (in $Rs.$) that must be marked on the camera,which cost him $Rs.\, 600$,to make a profit of $20 \%$ would be

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 $Rs.$).

If $Rs. 10$ is allowed as true discount on a bill of $Rs. 110$ due at the end of a certain time,then the discount allowed on the same amount due at the end of double the time is (in $Rs.$)