Only people with high IQs can work out how bill was split in pizza brainteaser

People have been left scratching their heads over a brainteaser all about pizza that 'almost everyone gets wrong' when they sit down to solve it. The puzzle has been shared on social media – and users have admitted to searching through the comments after failing to crack the code.

Taking to Quora, one user answered the question: "What's your favourite mathematical brainteaser most people are unable to solve?" Laying out the question, they said: "Three men go out for pizza. The bill comes to thirty pounds (£30). The three men each give the waiter a £10 note.

"The waiter returned to the kitchen only to be told that there had been a mistake and that the bill should have been £25. So they have been over paid by £5.

"The waiter realises that he does not know how to share £5 between three people. He also realised that the three men would appreciate any rebate.

"So he took£5 out from the till, put £2 in his pocket and gave the three men a £1 coin each.

"So each man paid £9 and the waiter kept two pounds. But three nines are 27, so adding the £2 in the waiter’s pocket gives a total of £29. So where is the missing £1?"

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Answer

While most people struggled to come up with the correct answer, others say you just need to turn the question on its head to answer it.

One user said: "It’s only confusing when you come at it backwards. There is no extra £1. The £30 they initially paid is the starting point. Waiter gives each of the three men £1 per, keeps £2 for himself, leaving £25 in the till.

Coming at it the other way, the extra £1 is still in the till. At £25 per pizza, each man’s share is 8.33. So if they get a refund of £1, they end up paying £9.33 per for the pie, which comes to £28. Add the £2 in the waiter’s pocket to get back to £30."

Another user added: "Okay. First off, if three pizzas cost £25, then each pizza is £8.3333. Each person got back 1 from the waiter, which made the sum to 9.3333 per head.

"Waiter chose to keep two, which amounts to an individual contribution of .6666. So individually each one's contribution is 9.3333+.6666= 10(after the round-off). There isn't anything missing."

While others complained about the wording of the question, a third user said: "Why are you adding that £2 tip given to the waiter in the total expense twice, if such is the case then you might as well add the cost of pizza too now it will come £27 paid by the 3 guys, £2 waiters tip and £25 for the pizza which comes to £54 , now the question is where did that extra £24 come from…. Now you can see that the question was framed wrong…."

The simple calculation is that each of them paid £9 which amounts to £27, out of which £25 was for the pizza and £2 for the tip.

As expected the riddle is meant to mislead you into believing 'three nines are 27, plus the £2 the waiter kept makes £29..." – however, there is no missing £1.

Instead, the common confusion comes from adding the £2 twice - once inside the £27, and then again outside it.