Black Hats and White Hats

In a dark room there were 3 black hats and 2 white hats. Three people, A, B and C were asked to go inside the dark room and put a hat on and then leave the room to stand in a queue. No body could see the color of their own hats. A stood in the front so he could not see B or C. B could see A but not C and C could see both A and B.
When C was asked if he could tell the color of his hat, the answer was "no." And so was the answer from B. However when the same question was asked of A the answer was "yes."
What was the color of A's hat? How did A figure this out?

Solution: Twelve Coins

Hint: First number the coins from 1 to 12, and divide them into 3 groups...

I first heard this puzzle from Anthony while Peter and I were visiting his antique shop in Grays Market in London. In the beginning I thought this should be easy. But I could not solve it there. I was still thinking about this puzzle when we were visiting the British Museum later on that day.

The next morning we were at the Heathow Airport waiting for our flight home. On a piece of paper I numbered the coins and started a flow chart of weighing results. The solution came and it was beautiful!

See the solution to the 12 coins puzzle.