Here's one to figure out
Three guys want to buy a second hand tv. They each put £10 in a kitty (=£30) and give it to a fourth guy. He goes to the shop and finds out the tv has been reduced to £25, so he buys it and gives the three guys £1 each back telling them it was reduced, and keeps the remaining £2 out of the fiver over. So, the three guys have only paid £9 each, the forth guy has £2.... NOW, 3 x £9 = £27. Forth guy has only £2, (= £29 total) where's the other pound?