If the cost price of $21$ watches is equal to the selling price of $18$ watches,then what would be the gain percent in this transaction?

$A$ shopkeeper allows a discount of $10\%$ on the marked price of an item but charges a sales tax of $8\%$ on the discounted price. If the customer pays $Rs. 3,402$ as the price including the sales tax,then the marked price is (in $Rs.$)

$A$ and $B$ started a business by investing $Rs. 3,50,000$ and $Rs. 1,40,000$ respectively. $A$ gets $20\%$ of the yearly profit for managing the business. Thereafter,the profit is divided in the ratio of the capital. If $A$ receives totally $Rs. 38,000$ more than $B$ at the end of a year,then the total profit is (in $Rs.$)

$A$ man buys $300$ dozen of bananas for $Rs. 3,600$. He sold $1/3$ of the stock at a loss of $10\%$ and the remaining $2/3$ of the stock at a gain of $10\%$. Find his overall percent profit or loss.

By what fraction selling price $(S.P.)$ must be multiplied to get the cost price $(C.P.)$ if the loss is $20 \%$?

Mohit lost $18 \%$ by selling a bicycle for $Rs. 1230$. What percent shall he gain or loss by selling it for $Rs. 1600$?