What rate of interest does a man get for his money when in discounting a bill due in $10 \, \text{months}$, he deducts $4 \%$ of the amount of the bill? (in $\%$)

The true discount on a bill of $Rs.\, 1260$ due for $6$ months at $10 \%$ per annum is (in $Rs.$):

The price of an article is cut by $42 \%$. To restore it to its original value,the new price must be increased by (in $\%$):

The true discount on a bill due $10$ months hence at $15 \%$ per annum is $Rs. 225$. The amount of the bill is (in $Rs.$)

If the simple interest on a certain sum for some years at $6 \%$ is $Rs. 180$,and the true discount at $5 \%$ on the same amount for the same time is $Rs. 140$,find the sum (in $Rs.$) and the time (in $years$).

$A$ 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 $\%$)