Eh, when you think about it, it makes sense. Original rules (host knows where car is and always opens a door with a goat): - 1/3 of the time your original cho

Eh, when you think about it, it makes sense. Original rules (host knows where car is and always opens a door with a goat): - 1/3 of the time your original choice is the car, and you should stick - 2/3 of the time your original choice is a goat, and you should switch Alternative rules (host doesn't know where car is, and may open either the door with the car or a door with a goat) - 1/3 of the time your original choice is the car, the host opens a door with a goat, and you should stick - 1/3 of the time your original choice is a goat, the host opens a door with a goat, and you should switch - 1/3 of the time your original choice is a goat, the host opens the door with the car, and you're going to lose whether you stick or switch So even under the new rules, you still only win 1/3 of the time by consistently sticking. You're just no longer guaranteed that you can win in any given game.