Comments by "bj0rn" (@TheLivirus) on "Numberphile" channel.

  1. Best explanation: There are two possibilities: (A) 1/3 chance that the car hides behind the door you picked. Both other doors are zonks, one of which has been opened. By switching you lose the car. (B) 2/3 chance that the car is behind one of the other two doors, one of which has now been opened, revealing no car. By switching you win the car. Hence, by switching you have a 2/3 chance of winning the car.
    6