Three friends have just finished eating a meal out in a cafe.  The
waiter says the bill is £30, so the guests split it evenly and pay £10 each.

Soon after they’d paid the waiter realises that he’s overcharged the friends
and the bill should only be £25.

To resolve the problem, he takes the £5 that is owed to the guests back to them in order to reduce the overall cost down to £25 but on the way back to the table, he realises that he cannot divide £5 equally between three people.

As the customers are still unaware of the actual total of the revised bill,
the waiter decides to give each of the three friends £1 each and then
keep the leftover £2 as a tip for himself.

So, each customer got £1 back, meaning they only paid £9 each,
bringing the total paid to £27. The waiter has £2.

The £27 the customers paid plus the £2 the waiter kept = £29.  Yet the friends
had originally handed over £30.

Mr Evitts, Maths Teacher