The cost price of $100$ books is equal to the selling price of $60$ books. The gain percentage or loss percentage is:

$A$ trader marks his goods $40 \%$ above the cost price and allows a discount of $25 \%$. The profit he makes,is in $\%$:

If the selling price of $\frac{2}{3}$ of a certain quantity of milk is equal to the cost price of the whole quantity of milk,then what will be the gain percent in this transaction?

Three successive discounts of $10 \%$,$12 \%$,and $15 \%$ are equivalent to a single discount of what percentage (in $\%$)?

$A$ man purchased some eggs at $3$ for $Rs. 5$ and sold them at $5$ for $Rs. 12$. Thus,he gained $Rs. 143$ in all. The number of eggs he bought is:

An article is sold at a profit of $20 \%$. If both the cost price and selling price are $Rs. 150$ less,the profit would be $5 \%$ more. Find the cost price.