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Three wise men, five hats, and the blind one knows

A king has five hats: three white and two black. He places one hat on each of three wise men, hides the other two, and tells them what the five hats were. The first two men can see each other and the third man, but not themselves. The third man is blind.

The king asks the first man: "What colour is your hat?" He replies, "I cannot tell." The second man is asked and, after thinking, also says, "I cannot tell." The blind man then says, "I know what colour my hat is."

What colour is the blind man's hat, and how did he work it out?

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What would the first man have seen if he could have answered? What does his failure tell the second man?

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