The present worth of a sum of money due for $146 \text{ days}$ at $5 \%$ is $Rs. 400$. The sum due is (in $Rs.$)

At what percent above the cost price must a person mark the price of an article so that he can enjoy $20 \%$ profit after allowing $20 \%$ discount?

$A$ $20 \%$ discount is offered on an item. By applying a promo code,the customer wins $30 \%$ cash back. What is the effective discount? (in $\%$)

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

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 $\%$):

$Rs. 21$ 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 $Rs.$)