There’s an old puzzle that I’ll present here for anyone who’s not come across it before:

3 friends go to a restaurant and have a nice meal. At the end the bill comes to £30. Each friend puts in £10 and they get up and leave.

A few minutes after they have left the restaurant owner realises he has overcharged them and the meals should have only cost £25. He takes 5 £1 coins out of the till and hands it to the waiter with instructions to find the men and give them their refund.

The waiter decides that splitting the coins between 3 people would be too fussy so he catches up to the men, gives then £1 each and keeps £2 as a tip for himself.

Each man has now paid £9 for their meal (£10 minus the £1 change)

3x£9 = £27

Add the £2 that the waiter kept and you get £29. Where has the last pound gone from the original £30 paid?

Scroll Down for the solution

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I’ve heard many possible explanations about where the £1 could have gone in the past (the waiter stole it?) But this problem only exists because of how the maths has been presented.

The solution comes from realising that the wording of the puzzle is slightly incorrect and that the waiters tip is already included in the £27 (£25 meal + £2 waiters tip)

The last £3 comes from the refund that the waiter has given back. So the total breakdown of the night is

  • £25 meal
  • £2 waiters tip
  • £3 refund
  • = £30 total