Another Hat Puzzle

If you enjoyed trying out the Four Men in Hats puzzle, here's another one for you. Again, the inmates must solve the puzzle or they will be executed.


On one such occasion, three cells were needed, so three of the cleverest inmates - Albert, Barry, and Carl - were put in a room and given a challenge. A guard showed them 5 party hats - 3 white, 2 black.  The guard then removed the hats from view, walked behind each prisoner and placed a party hat on his head.  Each inmate could see the two other inmates' hats, but not his own; nor could he see the two extra hats that were not placed on heads.

The guard said, "If anyone can tell me with absolute certainty the color of his own hat, you may all go free.  However, under no circumstances may you communicate the color of anyone else's hat."

He first asked Albert.  Albert is a very honest and intelligent (ie perfectly rational) person, but he was dumbfounded.  "I don't know", he said, "there's no way of knowing."

He then asked Barry.  Barry was equally intelligent and rational, but he also could not say.

The guard said, "I regret that I have to execute you three, but seeing as Carl is blind, he's not going to know.  You have failed."

But ...Carl knew what color hat he wore! How could that be? The answer is posted at The Weekly Riddle. Link -via a comment at Geeks Are Sexy

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If the blind man was wearing black then the only way the first guy would have not been able to guess his own correctly, is if the second guy was wearing white (two black hats would have given him his own color). When the second guy came to guess he would have seen the blind guy's black hat and thought "Hey, I must be wearing a white hat then, otherwise the first guy would have got it.". As neither of them were able to guess their own hat color, then the blind man knew he must be wearing a white hat.
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The solution resides in eliminating all situations in which Albert and Berry would have answered differently... and especcially which informaiton Berry gets from Alberts answer...
However Josh's objection may be overcome if the guard just tells what he has in his hands and what he does,...
The funny thing is that he still may not tell the colour of even one of the others inmate's hats..
I did not know this riddle so found it challenging..
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Aha! A detail that matters! For the answer to work, Carl would have to know how many of each there were, so someone would have to have told him. They kept that part about Carl being blind until the end of the question to throw the reader off, I guess.
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