Brain Busters

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Posted:
in AppleOutsider edited January 2014
There's a wall.



On one side of the wall you have a guy with a black hat. He can't see over the wall.



On the other side of the wall, you have three guys in a line with hats. The one closest to the wall has a white hat. The middle one has a black hat. The last one has a white hat. They can't turn around. The 4 also can't say anything unless they know with 100% certainty what color hat they have on. There can only be 2 black hats and 2 white hats. The last one in line can see the two people ahead of him, so he knows which color hats they have on.



Which one knows with absolute certainty which color hat he has on?



(No cheating, internet savvy forum members!)



*Also, share some brain busters of your own!

Comments

  • Reply 1 of 11
    dmzdmz Posts: 5,775member
    Can any of the other three see the one guy with the black hat?
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  • Reply 2 of 11
    shawnjshawnj Posts: 6,656member
    Quote:
    Originally Posted by dmz View Post


    Can any of the other three see the one guy with the black hat?



    Only the guy at the end of the line can see a guy with a black hat.



    (Again, note that he can see the two guys in front of him, so he knows what color hat they have on)
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  • Reply 3 of 11
    addaboxaddabox Posts: 12,665member
    And no body can take their hat off or anything like that, right?
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  • Reply 4 of 11
    shawnjshawnj Posts: 6,656member
    Quote:
    Originally Posted by addabox View Post


    And nobody can take their hat off or anything like that, right?



    Right.



    Just the facts listed.
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  • Reply 5 of 11
    addaboxaddabox Posts: 12,665member
    So I'd say it has something to do with the fact that the guy on the far side doesn't hear anyone speak up, so he knows the last guy in the line of three is seeing a white and black hat in front of him.



    Oh, wait, the second guy in line knows that too, and he can see the white hat in front of him, so he knows he must be wearing the black hat.
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  • Reply 6 of 11
    shawnjshawnj Posts: 6,656member
    I'll let dmz take a crack at it too.
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  • Reply 7 of 11
    dmzdmz Posts: 5,775member
    Quote:
    Originally Posted by ShawnJ View Post


    Only the guy at the end of the line can see a guy with a black hat.



    (Again, note that he can see the two guys in front of him, so he knows what color hat they have on)



    I think addabox got it. It's the only way for the last guy to be up in the air. He knows the last guy is confused because he (himself) can't be wearing a white hat.
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  • Reply 8 of 11
    hardeeharharhardeeharhar Posts: 4,841member
    definitely the middle guy... after about thirty seconds...
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  • Reply 9 of 11
    addaboxaddabox Posts: 12,665member
    And, by the conditions set, the first guy in line will know he has a white hate as soon as the guy behind him speaks up.



    Which means the first guy will definitely know what color hat he is wearing, as well.



    Last guy in line and guy on other side of wall are doomed to a life of ambiguity, however.
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  • Reply 10 of 11
    shawnjshawnj Posts: 6,656member
    Quote:
    Originally Posted by dmz View Post


    I think addabox got it. It's the only way for the last guy to be up in the air. He knows the last guy is confused because he (himself) can't be wearing a white hat.



    Right!



    Who's got a good brain buster?



    I know hardeeharhar's got one that will stump us all.
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  • Reply 11 of 11
    SpamSandwichspamsandwich Posts: 33,407member
    To paraphrase The Matrix... "there is no hat".
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