Question about the movie 21

I'm really dumb at math but the way I see it, is since they open door No.3 and there is a goat there, they obviously couldn't open door number one and have a goat there, because he already picked door no. 1.

So we know there was a 67 percent chance of a goat between doors 2 and 3. Now that three is showing, there is a 33 percent chance of a goat in No.1 and No.2, so switching the door gives you a 67 percent chance of being right.



Either that or I am thoroughly confused.

 

Goddammit, I've been looking everywhere for that damn goat.

 

Try box seats at Yankee Stadium.

 

From Wiki...

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. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice?

• Choose which of the three doors has a car. (33% chance of being correct)
  
  You choose door 1.
  
  I show you door three has a goat.
  
  So now there are two doors, and one has a car.
  
  There is no reason to change your choice.
  
  You how have a 50% of finding the car.

It's a great question because it shows the character of the person changing doors or not changing doors.

 

You're right. The key to the puzzle is when the host (who knows the answer) shows you a goat. At that point, the answer becomes easier to see.

 

When you picked door No. 1, you had a 67 percent chance of being wrong. When door No. 3 is revealed to show the goat, that doesn't change the probability that you were wrong. Therefore, door No. 2 is the right choice 67 percent of the time.

 

This sentence makes no sense to me.

Please read it very slowly.

 

Yes, once one is eliminated, it DOES increase your chances you are right.

 

No, it doesn't. I know you like to argue, but I am going to pull rank here. I took calculus in ninth grade. You switch to door No. 2 because you have a 67 percent chance of being right. This is a mathematical certainty. I will not address it again.

 

You are both right .. one is speaking from the positive (33 percent likelihood of being correct), while another is speaking about the negative (66 percent likelihood of being wrong) ... two sides of the same equation.

 

No, only one of us is right.

 

66.667, asshole.