One day, Mammu, home from school set a very interesting problem to me. She pushed a large circular table we have at home, into the corner of the room, so that it touched both walls and spilled a spot of ink on the extreme edge, and she said, “Mummy here is a little puzzle for you. Look at that spot. It is exactly eight inches from one wall and nine inches from the other. Now tell me the diameter of the table without measuring it”. Can you?