Question: There are four men: Abe, Butch, Cam, and Dan. There are four hats: two white and two black. They each get a hat: Abe gets black, Butch gets white, Cam gets black, and Dan gets white. They don't know what hat color they have. Abe goes into a room so that no one can see his hat. The others line up in front of the door in the order Butch, Cam, and Dan (Butch can't see the others hats, Cam can see Butch's, and Dan can see Cam and Butch's hats). Whoever can figure out their hat color first wins $1,000. If they are wrong they are out of the running.
Which man can figure out his hat color without a doubt?
Answer: Cam can figure it out. If Dan saw that Cam and Butch had the same color hat he would know his hat color. Since he doesn't quickly figure out his hat color, Cam knows that him and Butch don't have the same hat color. So all he has to do is say that his hat color is the opposite of Butch's hat color (after giving enough time to be sure that Dan doesn't know his own color).