Three ladies go to a restaurant for a meal. They receive a bill for £30. They each put £10 on the table, which the waiter collects and takes to the till. The cashier informs the waiter that the bill should only have been for £25 and returns £5 to the waiter in £1 coins. On the way back to the table the waiter realizes that he cannot divide the coins equally between the ladies. As they didn’t know the total of the revised bill, he decides to put £2 in his own pocket and give each of the ladies £1.

Now that each lady has been given a pound back, each of the ladies has paid £9. Three times 9 is 27. The waiter has £2 in his pocket. Two plus 27 is £29. The ladies originally handed over £30. Where is the missing pound?