A riddle of three friends each throwing in an equal amount to settle a bill sounds pretty simple, right? But a video shared on TikTok has racked up thousands of comments from users left scratching their heads at the conundrum. The riddle: Three friends go out for dinner at a restaurant and they split the bill, each throwing in £10, making a total of £30. The meal only came to £25 so the waiter has to give them £5 in change. Unsure of how to split it equally between the three customers, he gives them each £1 back, and he keeps £2 for himself. After the friends are given £1 back, they have now only paid £9 each instead. That makes £27, plus the £2 the waiter kept, making £29. So where has the extra pound gone? The answer: The pound is not missing at all, and the riddle is an example of informal fallacy, meaning the error lies in the reasoning. The trick comes in the wording of the riddle, where it suggests adding the £2 the waiter kept to the £27 the friends have paid. The £2 for the waiter has already been included in the £27 total, as the bill was originally only £25. Then add on the £3 given to each of the friends to the total of £27 and it all starts to make a lot more sense. £25 + £1 + £1 + £1 + £2 = £30.