pmsumner

Annoyingly, I knew I had read it not too long ago, yet couldn't remember nor figure out the answer. I had an inkling it was (C) but couldn't be sure...

The King of Syracuse summoned the three wisest men in his kingdom in order to find out which was the absolute wisest. He blindfolded them all, and then put a hat on each man's head.

`In a minute,' he said, `I want you all to remove your blindfolds. Your hats are either black or white. If you can see any black hats, put your hand up. As soon as you know what colour your hat is, say so.'

The men removed their blindfolds. Each man could see the other men's hats, but no man could see his own hat. All three hats were in fact black, so all the men put their hands up.

After a minute, the wisest man put his hand down and said `My hat is black'. How did he know?

All men raise their hands, so everybody must be able to see at least one black hat.

The wise man (and the other two) can see two black hats.

If one of them could see a white hat and a black hat, they would know that their own hat were black. This is because the person they can see with the black hat has his hand up - indicating that he can see a black hat. If they were wearing a white hat as well as the visible person wearing a white hat, the black hatted person would not raise his hand.

However, no-one appears to know the answer at first. This suggests that none of them are wearing white hats, assuming that all 3 were capable of the reasoning as above. Hence the wise man correctly guesses that he is also wearing a black hat.Thanks to Kyte for the explanation I nicked from Mono

Not quite the same as the one we were given today, but close enough and has the same reasoning behind it. Damn annoying because I knew I knew I KNEW I knew it.