Question: Three convicts are brought into the warden's office. He says he can parole one of them and to decide which one he will parole he takes out 5 hats (3 red and 2 white). He stands behind them and places a hat on each one of their heads and puts the other two remaining hats in a drawer.
He tells the prisioners they can look at the others hats and if they can tell which hat they have on they will be the one who is paroled.
The first man looks at the other two and says, "I don't know."
The second man looks at the others hats and says, "I don't know."
The third man who is blind says, "Even though I have not the gift of sight I can tell by what the others have said that the color of my hat is..."
What color is the blind mans hat and how does he know?
Answer: The color of blind man's hat is Red.
It is sure that the first man saw either both Red hats or one White hat and one Red hat. There are 6 such possibilities:
1) R R R
2) R R W
3) R W R
4) W R R
5) W R W
6) W W R
In all above possibilities, the first man won't be sure of the color of his hat.
Now, the second man knows that the first man saw either both Red hats or one White hat and one Red hat. And, he also knows that its one of the above 6 possibilities. (like we know ;)) But he says, "I don't know". That means that (2) and (5) are not the possibilities as in either case he would be sure of the color of his hat (Red) by just looking at the third man's color of hat (White).
Now, the blind man knows that there are just 4 possibilities - (1), (3), (4), (6) - and in all, the color of his hat is Red.