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

$A$ 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 $8 \%$.

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?

$A$ trader allows a trade discount of $20 \%$ and a cash discount of $6 \frac{1}{4} \%$ on the marked price of the goods and gets a net gain of $20 \%$ of the cost. By how much above the cost should the goods be marked for the sale? (in $\%$)

$A$ cloth merchant sold half of his cloth at $20 \%$ profit,half of the remaining at $20 \%$ loss,and the rest was sold at the cost price. In the total transaction,his gain or loss will be

Find $SP$ when $CP = Rs. 80.40$ and $\text{loss} = 5\%$.