This is an old one, but still one of my favorites:
There is a vacancy for the job of Apprentice Logician and there are three applicants.
The Master Logician has the three candidates enter a room which has no mirrors. He tells them "I have here a box with three black hats and two white hats. In a minute I will blindfold you and put one of these hats on each one of your heads, removing the other two. Then I will remove the blindfold and leave the room. The first person to deduce (correctly) the colour of his own hat must knock on my door, tell me why, and he will get the job".
Since he is a very fair person and wants each to have an equal chance, he puts a black hat on each candidate.
The three look at each other,for a while and after about a minute one gets up and knocks on the door.
How did he reason?
Originally posted by CalJustYou give too much away.
This is an old one, but still one of my favorites:
There is a vacancy for the job of Apprentice Logician and there are three applicants.
The Master Logician has the three candidates enter a room which has no mirrors. He tells them "I have here a box with three black hats and two white hats. In a minute I will blindfold you and put one of these hats on ...[text shortened]... r,for a while and after about a minute one gets up and knocks on the door.
How did he reason?
The Master can put any hats on them and it is
possible for one Apprentice to deduce what hat he has.
The problem can be expanded to any number
ie N apprentices, N black hats, (N-1) white hats
Originally posted by AThousandYoungI gather the dude figured it out because the others could not, nor would he if he was in their shoes. Not sure what that leaves ME though🙂
Next hint.
We see two black hats.
What are the possibilities?
1) I have a black hat.
2) I have a white hat.
What do the others see?
Either,
1) two black hats or
2) one white, one black
Originally posted by KewpieAs I said, the Master is fair, so everybody had the same chance.
I'm sure he's wearing a black hat, but I'm having trouble writing out the reasoning. If the other two don't know what they're wearing, they must be seeing just what he's seeing. But I don't think that makes sense.
But that is not a good enough reason to say "my hat must be black".
The point of departure is to say: "I can only have a black or a white hat. Let's assume my hat is white. What would be the consequences?"
Looks like nobody is interested, si I will give the answer anyway.
Let's call the applicants A, B and C.
A thinks: "I could have a white hat or a black one.
If I had a white one, B would see one white and one black hat.
So B would know that if he (B) had a white hat, then it would take C only a split second to figure out that he (C) had a black hat, since both white ones would have been accounted for. But C does not move, so B cannot have a white hat. So B would immediately know that he (B) had a black hat."
But B dies not move, hence A cannot have a white hat.
Ergo, A has a black hat.
