Three guys go into a cafe and order lunch. They have a great lunch and the bill comes.
It totals £30. They each pay £10 and the waiter takes the money to his boss.
The boss advises him that they have over paid and the bill should have been £25 so he gives the waiter £5 to give back to the customers.
On the way back to the table the waiter decides, as the customers did not know about the overcharging, to keep two pounds and give them back a pound each.
So they each have now paid £9 and the waiter has kept £2
3x £9 = £27 + £2 for the waiter = £29
Where did the missing £1 go?
Dunc