A fruitseller sells mangoes at the rate of $Rs.\, 9$ per $kg$ and thereby loses $20 \% .$ At what price per kg he should have sold them to make a profit of $5 \% ?$ (in $Rs.$)

A shopkeeper sold an article offering discount of $5 \%$ and earn a profit of $23.5 \% .$ What would have been the percentage of profit earned if no discount has been offered?

The cost price of $6$ pens is equal to the selling price of $4$ pens. Find the profit percent.

A shopkeeper purchased a chair marked at $RS.\, 600$ at two successive discounts of $15 \%$ and $20 \% .$ He spent $Rs.\, 28$ on transportation and sold the chair for $Rs.\,545.$ His gain percent was

Abhishek makes a profit of $Rs.\,110,$ if he sells a certain number of pens he has at the price of $Rs.\, 2.5$ per pen and incurs a loss of $Rs.$ $55,$ if he sells the same number of pens for $Rs.$ $1.75$ per pen. How many pens does Abhishek have?

If the discount of $10 \%$ is given on the marked price of a radio, the gain is $20 \%$. If the discount is increased to $20 \%,$ the gain is......$\%$