A friend asked me this question, the other day - A lady buys goods worth Rs. 200 from a shop. (shopkeeper is selling the goods with zero profit). The lady gives him Rs. 1000 note. The shopkeeper gets the change from the next shop and keeps Rs. 200 for himself and returns Rs. 800 to the lady. Later the shopkeeper of the next shop comes with the Rs. 1000 note saying "duplicate" and takes his money back. How much LOSS did the shopkeeper face? The answers that people came up with were - Rs. 1000, Rs. 2000, Rs. 1800, Rs. 1200 and Rs. 800 If you are going to reply with an answer, please provide a detailed solution.