On an order of $5$ dozen boxes of a consumer product, a retailer receives an extra dozen free. This is equivalent to allowing him a discount of........$\%$

Anil bought an item with $12 \frac{1}{2} \%$ discount on the labellea price. He sold the item with $17 \frac{1}{2} \%$ profit on the labelled price. What was, his percent profit on the price he bought?

Peter purchased a machine for $Rs$ $80000$ and spent $Rs. 5000$ on repair and $Rs.\, 1000$ on transport and sold it with $25 \%$ profit. At what price did he sell the machine? (in $Rs$)

When a book is sold at its Marked Price it gives a profit of $40 \% .$ What $\%$ will happen if it is sold at half the marked Price?

A cab driver makes a profit of $20 \%$ on every trip when he carries $3$ passengers and the price of petrol is $Rs.\,30$ a litre. Find the percentage profit for the same journey if he goes with four passengers per trip and the price of petrol reduces to $Rs.\, 24$ a litre? (in $\%$)

(Assume that revenue per passenger is the same in both the cases.)

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