Memo to Carleton Fiorina: Read the book. Twice if you have to.
Three men decide to buy a second-hand black and white TV set. They find the one they want. It's £30, £10 each. After they've left the shop, the manager returns and tells his assistant that the TV should have been £25, not £30, and instructs him to give them back £5. On finding the men, the assistant realises that £5 does not divide evenly three ways. He thus gives each man £1 and pockets the remaining £2. They have now paid £9 each. Three times £9 equals £27, plus the £2 that the assistant kept totals £29. So what happened to the other £1?