By selling $90$ pens for $Rs. 80$,a man loses $20\%$. What should be the selling price (in $Rs.$) of $90$ pens for $20\%$ profit?

By selling an article at $80 \%$ of its marked price,a shopkeeper makes a loss of $10 \%$. What will be the profit percentage if he sells it at $95 \%$ of its marked price (in $\%$)?

The marked price of a watch was $Rs. 720$. $A$ man bought the same for $Rs. 550.80$ after getting two successive discounts,the first being $10 \%$. The second discount rate is.......$\%$

If an item is sold for $Rs. 924$,there is a profit of $10\%$. What is the cost price?

The marked price of a clock is $Rs. 3200$. It is sold at $Rs. 2448$ after two successive discounts. If the first discount is $10 \%$,then the second discount is.........$\%$

$A$ trader marked his goods at $20 \%$ above the cost price. He sold half the stock at the marked price,one quarter at a discount of $20 \%$ on the marked price,and the rest at a discount of $40 \%$ on the marked price. What is his total gain percentage?