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?

The ratio between the selling price and the cost price of an article is $7:5$. What is the ratio between the profit and the cost price of that article?

$A$ shopkeeper labeled the price of his articles in order to earn a profit of $30 \%$ on the cost price. He,then,sold the articles by offering a discount of $10 \%$ on the labelled price. What is the actual rate of profit he earned in the deal? (in $\%$)

If a radio is purchased for $Rs. 490$ and sold for $Rs. 465.50$,find the $\text{loss} \%$. (in $\%$)

$A$ sells an article to $B$ making a profit of $\frac{1}{5}$ of his outlay. $B$ sells it to $C$,gaining $20\%$. If $C$ sells it for $₹ 600$ and incurs a loss of $\frac{1}{6}$ of his outlay,the cost price of $A$ is (in $₹$):

$A$ dishonest dealer uses a scale of $90 \, cm$ instead of a metre scale and claims to sell at cost price. His profit percentage is: