 
Summary: Probability paradoxes
Helmer Aslaksen
Department of Mathematics
National University of Singapore
aslaksen@math.nus.edu.sg
www.math.nus.edu.sg/aslaksen/sfm/
1
The Car and Goat Game
You're on a game show and you're faced with
three doors. Behind one of them is a car.
You're asked to pick a door, and you choose
door 1. Before the host opens it, she first
opens door 2, and you see that there's noth
ing behind it. She then asks you if you are
sure about door 1, or if you want to switch
your guess.
Suppose you pick door 1 and that the host
opens door 2. The probability that the car
is behind 1 is 1/3, so you're probably wrong,
but after the host opened door 2, you know
