Successive discounts of $10 \%$,$20 \%$,and $30 \%$ are equivalent to a single discount of (in $\%$):

$Rs. 20$ is the true discount on $Rs. 260$ due after a certain time. What will be the true discount on the same amount due after half of the earlier time,the rate of interest being the same? (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 $years$)

Ramesh marks his goods $30 \%$ above cost price. If he sells the item for $Rs. 910$ after allowing a discount of $15 \%$,find his cost price (in $Rs.$).

The true discount on a bill of $Rs. 720$ is $Rs. 80$. The banker's discount is (in $Rs.$)

$A$ trader marks the sale price $25\%$ more than the cost price and gives a $10\%$ discount at the time of selling. The gain percent is (in $\%$)