Problem
The Problem
A king has 3 wise men. He places a hat on each one's head, drawn from a collection of 3 white hats and 2 black hats. Each wise man can see the others' hats but not his own.
The king asks each in turn: "Do you know the color of your hat?" Each can answer "yes" or "no" (truthfully). The first says "no", the second says "no", the third says "yes" — and correctly states his hat color.
What color is the third wise man's hat, and how does he know?