By selling $100$ oranges,a vendor gains the selling price of $20$ oranges. His gain percent is

Abhishek makes a profit of $Rs. 110$ if he sells a certain number of pens 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 a man reduces the selling price of a fan from $Rs. 400$ to $Rs. 380$,his loss increases by $2 \%$. The cost price of the fan is (in $Rs.$)

$A$ loss of $19 \%$ gets converted into a profit of $17 \%$ when the selling price is increased by $Rs. 162$. The cost price of the article is (in $Rs.$)

By selling $25$ $metres$ of cloth,a trader gains the selling price of $5$ $metres$ of cloth. The gain of the trader in $\%$ is:

$A$ cloth dealer professes to sell cotton at cost price, but uses a meter scale having a length of $80 \, cm$ only and charges for a full meter. Find his gain percent.