1.Previous
3.Next

door 2 or door 3, so the probability that the car is behind door 1 and the host opens door 3 is × = . If the car is behind door 2 – with the player having picked door 1 – the host must open door 3, such the probability that the car is behind door 2 and the host opens door 3 is × 1 = . These are the only cases where the host opens door 3, so if the player has picked door 1 and the host opens door 3, the car is twice as likely to be behind door 2 as door 1. The key is that if the car is behind door 2 the host must open

1.Previous
3.Next