Oranges are bought at 6 for Rs.20 and sold at 4 for Rs.18. Find the gain or loss per cent.

By selling 130 cassettes, a man gains an amount equal to the selling price of 5 cassettes. Find the gain per cent.

By selling 45 lemons, a vendor loses a sum equal to the selling price of 3 lemons. Find his loss per cent.

A vendor purchased bananas at Rs.40 per dozen and sold them at 10 for Rs. 36. Find his gain or loss per cent.

A man bought apples at 10 for Rs. 75 and sold them at Rs.75 per dozen. Find his loss per cent.