A bit late to the party (came from Hacker Newsletter) but it seems obvious to me: - If you happen to choose a door with a goat (⅔ of the time), the host has to

A bit late to the party (came from Hacker Newsletter) but it seems obvious to me: - If you happen to choose a door with a goat (⅔ of the time), the host has to choose a goat door, leaving "switch" a guaranteed win - If you happen choose the door with the car (⅓ of the time), the host opens a random goat door and you have 50/50 between staying and switching So always switching is the correct move - if you do that you'll win the ⅔ of the time (every time you open a goat door).