(medium) 2 goat and car

Jun 6, 2009 4:40 PM

Offline

Feb 2008

This is that puzzle in the movie 21:
You are on a game show and there are three doors. The presenter tells you that behind one of doors there is a car and behind the other two are goats. If you pick the car you win it.
After you have picked a door the presenter opens a different door with a goat behind it, he then gives you the chance to change what door you open. What should you do?

It's not 1/2 chance.

Sep 19, 2009 4:47 PM

dosithee

Offline

May 2009

Not having seen 21 and confused by your explination, I have copied a full version from wikipedia. The original name of the puzzle is the Monty Hall Problem.
"Suppose you're on a game show and you're given the choice of three doors. Behind one door is a car; behind the others, goats. The car and the goats were placed randomly behind the doors before the show. The rules of the game show are as follows: After you have chosen a door, the door remains closed for the time being. The game show host, Monty Hall, who knows what is behind the doors, now has to open one of the two remaining doors, and the door he opens must have a goat behind it. If both remaining doors have goats behind them, he chooses one randomly. After Monty Hall opens a door with a goat, he will ask you to decide whether you want to stay with your first choice or to switch to the last remaining door. Imagine that you chose Door 1 and the host opens Door 3, which has a goat. He then asks you "Do you want to switch to Door Number 2?"

Feb 7, 2010 5:42 PM

GreatEmperor