$A$ fruit vendor buys $10$ bananas for $Rs. 14$ and sells them at $12$ for $Rs. 15$. Find his percentage gain or loss.

$A$ shopkeeper loses $7 \%$ by selling a cricket ball for $Rs. 31$. For how much should he sell the ball so as to gain $5 \%$? (in $Rs.$)

$A$ shopkeeper has to sell $24 \text{ kg}$ of sugar. He sells a part of these at a gain of $20 \%$ and the rest at a loss of $5 \%$. If on the whole he earns a profit of $10 \%$,what is the quantity of sugar (in $\text{kg}$) sold at a loss?

If the selling price of $40$ articles is equal to the cost price of $50$ articles,the loss or gain percent is

Raman sells a machine for $Rs. 39$ lakh at a loss. Had he sold it for $Rs. 49$ lakh,his gain would have been three times the loss. What is the cost price of the machine? (in $Rs. \text{ lakh}$)

The cost price of $6$ pens is equal to the selling price of $4$ pens. Find the profit percent. (in $\%$)