You have 3 boxes. One of them contains a prize. You were allowed to pick just one of them.
You pick - and it's empty.
With 2 boxes left, you now have one box in your hand and another box in front of you. If given the chance to exchange your box with the box in front of you, would you do it? Why, and why not?
(The 'Google Riddles' are interview questions those who wish to get hired were asked).
In the beginning, with 3 boxes, things were simple. You had a chance of 1 in 3 to find the prize. NOW we know that one of the boxes is empty but you still made a guess of 1 in 3, now you have a new choice of 1 in 2. Your probability goes up and that is why you SHOULD CHANGE THE BOX.
Don't feel bad if you disagree, this riddle has been hotly debated.