monty hall problem with 4 doors

Question

Explain the Monty Hall problem in the case of 4 doors computing specific probabilities.

Answer 1

Here’s the way to visualize the 3-door situation:
http://en.wikipedia.org/wiki/Monty_Hall_problem#Vos_Savant

Extending it to 4 doors (you choose 1, host opens any x):

1 2 3 4 Stay Switch-1 Switch-2
C x x x   C        x            x
x C x x   x        C            x
x x C x   x        C            x
x x x C   x        C            x

If you stay the probability you win the car is 1/4;

but if you switch the probability is 3/8.