At a party, four people played a game. Three of them sat one behind the other, so that Abe saw Bill and Cal, and Bill only saw Cal, who sat in front and saw nobody else.
Dave had 5 hats which he showed to his three friends. Three of the hats were blue and two were red.
Now Dave placed a hat on the head of each of his three friends, putting aside the remaining two hats.
Then he asked Abe what color his hat was.
Abe said he couldn’t tell.
Bill was asked the color of his own hat, but he didn’t know for certain either.
Cal, though he couldn’t see any hat at all, gave the right answer when asked what color his hat was.
Do you know what color Cal’s hat was and how he reasoned to find out the correct answer?