The banker's gain on a sum due $2$ years hence at $10 \%$ p.a. is $Rs. 120$. The banker's discount is (in $Rs.$)

$1$ packet of biscuits costs $Rs.\, 16$,but a pack of $4$ of the same packets of biscuits costs $Rs.\, 56$. What is the effective discount (in $\%$) on the pack?

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 $\%$).

$A$ retailer marks up his goods by $150 \%$ and offers a $40 \%$ discount. What will be the selling price (in $Rs.$) if the cost price is $Rs.\, 800$?

The $B.G.$ on a certain sum due in $5 \text{ years}$ is $\frac{3}{23}$ of $B.D.$ Here,the rate of interest is (in $\%$):

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