We have three children and we show them three red and two green hats. We put them in a row and put each one a hat on their head, so that the first one cannot see any hat, the second one sees one and the third one two, then we tell them that the first one to guess what color their hat is , you will have a bag of prize treats.
How is it possible for one to guess the color of his hat?
The first child, who sees no hat, guesses its color.
The conclusion he reaches is the following: Since the third child sees two hats and says nothing, it means that he does not see two green hats, since he would deduce that his is red. If the second one saw a green hat in front of him, the first one would know that his must be green, since he does not hear the third party say that he has a red one. Therefore the first deduces that his is red.