I needed to say that, because I'm about to admit to yet another embarrassing deficit. When I was very young, I owned a book of puzzles, and one of them stumped me. It went like this....
Three men check into a hotel, and are charged £30 pounds in total for three single rooms. They pay the money and go to their rooms, but the receptionist later realizes that they should only have been charged £25 between them (it was a special offer). She calls the porter over, hands him the extra £5, and tells him to refund the guests. The porter however, confused no doubt the difficulty of dividing £5 in three, decides to pocket £2 and hand over £1 each to the guests.
So, in effect the guests have each paid £10-1=£9 (i.e. £27 in total), and the porter has pocketed £2, making £29. What happened to the extra pound?
I'd totally forgotten this puzzle, and the frustration it caused me, until I read it again the other day. It's driving me crazy! Put me out of my misery, someone.