The banker's gain on a certain sum due in $2 \text{ years}$ at $5 \%$ per annum is $Rs. 8$. The present worth is (in $Rs.$)

$Rs. 21$ 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 $Rs.$)

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

$A$ owes $B$ $Rs. 1350$ due in $3$ months and $B$ owes $A$ $Rs. 1078$ due in $5$ months. If they agree to settle their account right now at $5\%$ $p.a.$ simple interest,how much should $A$ pay to $B$ (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 $\%$)