$A$ person purchases $8$ pens for ₹ $10$ and sells $10$ pens for ₹ $8$. How much profit or loss percentage does he make?

$A$ person sells $36$ oranges for $₹ 1$ and makes a loss of $4 \%$. Find how many oranges per $₹ 1$ should be sold to have a gain of $8 \%$.

With a $5 \%$ discount on the cost of sugar,a buyer could purchase $2 \text{ kg}$ more sugar for $Rs. 608$. What is the initial selling price of sugar per kg?

By selling an article for $Rs. 102$,there is a loss of $15 \%$. When the article is sold for $Rs. 134.40$,the net result in the transaction is:

In a certain store, the profit is $320 \%$ of the cost. If the cost increases by $25 \%$ but the selling price remains constant, approximately what percentage of the selling price is the profit?

$Mr.$ $A$ sold goods to $Mr.$ $B$ at a $10\%$ discount on the printed rate. The discounted value is $Rs. 1242$. If a $15\%$ profit is earned on the purchase rate by selling the goods at the printed rate,what is the purchase rate? (in $Rs.$)