$A$ person sells $36$ apples per rupee and suffers a loss of $4 \%$. Find how many apples per rupee should be sold to have a gain of $8 \%$.

$A$ vendor bought toffees at $6$ for a rupee. How many for a rupee must he sell to gain $20 \%$?

$A$ sold a pen to $B$ at a profit of $20\%,$ $B$ sold the same pen to $C$ for $Rs.\,75$ thereby making a profit of $25 \% .$ Find the price at which $A$ bought the pen? (in $Rs.$)

By selling $25$ $metres$ of cloth,a trader gains the selling price of $5$ $metres$ of cloth. The gain of the trader in $\%$ is:

$A$ man buys a table and a chair for $Rs. 500$. He sells the table at a loss of $10\%$ and the chair at a gain of $10\%$. He still gains $Rs. 10$ on the whole. The cost price of the chair in rupees is

$A$ shopkeeper purchased $70$ $kg$ of potatoes for $Rs. 420$ and sold the whole lot at the rate of $Rs. 6.5$ per $kg$. What will be his gain percent?