This was on the Simon Mayo R2 show this evening. I understood the maths of the problem, but not the answer that was given.
The story is that three men check into a hotel for the night. The room rate is $30, so they pay $10 each. Once they've gone up to the room, the receptionist realises that he's overcharged them as the room rate should only be $25. Because they've paid separately, he realise he can't refund them equally, so he gives them back one dollar each and pockets the other two himself.
So now they've each paid $9 dollars for the room, a total of $27, and the receptionist has kept $2, making $29 in all. So where's the missing dollar?
The guy on the radio explained why this thinking was mathematically wrong, but I couldn't get my head round it. Can anyone explain in idiot language, please?
It's a nonsensical calculation because there is absolutely no logic in adding the 27 to the 2. The hotel has $25, the receptionist has $2 and the men have $3- so all $30 is accounted for.
The three guys have each paid $9, which is $27 all right, but the $2 that the receptionist kept is PART OF that $27. So if you add it instead of subtracting it, you get $29 which completely illogically consists of $25 plus another $2 counted twice. Since that's an illogical sum, then whatever you try to compare it with, it is sure to turn out nonsense of one kind or another.
I remember this one from my childhood, only it was three men in a restaurant paying for their meal. This was before decimal currency when a pound was exactly divisible by three.
Sorry, we can't find any related questions. Try using the search bar at the top of the page to search for some keywords, or choose a topic and submit your own question.