Three students spend £30 (£10 each) on pizza. When the pizza boy returns to the restaurant, his boss points out they should only have paid £25 between them. He takes £5 back, but helps himself to £2 and gives the students back £1 each. The students have now paid £9 each making a total of £27. If the boy has kept £2, where did the extra pound go because £27 + £2 = £29
Each student paid with a £10 note so when the delivery boy handed it to the store, he was told that as pizzas were on offer he was given back five £1 coins. As he kept £2 for himself and gave each student £1 it still remains a puzzle as each student had now paid £9 = £27 plus the £2 kept by the delivery boy totals £29. Where did the other pound go?