Monty Hall Math Problem

I’m stealing this sort of from Joe Posnanski’s blog. I’ll change the wording up a bit to shorten it and remove the baseball content.

You are a contestant on Let’s Make A Deal. OK, so, there are three curtains. Behind one is new car and behind the other two are goats.

You choose your curtain for simplicity, we’ll say that you choose what’s behind Curtain No. 1. And Monty goes, “Well, before we see what’s behind your curtain, let’s show you what’s behind Curtain No. 3!” They pull back the curtain and there is a goat grazing on a square of sod held on a leash by a model.

Now, Monty gives you an option. He says that you can stay with Curtain No. 1 or switch to Curtain No. 2.

So what do you do?

A: Stick with Curtain No. 1.
B: Switch to Curtain No. 2
C: It doesn’t matter because there is an equal chance the prize is behind either curtain.

The correct answer is B. You ALWAYS switch. If you switch, you are twice as likely to get the big prize.

I thought C, there are two curtains, one has the prize, so you have a 50-50 shot. I read his original post, and the next day’s about it, and still couldn’t see my way to believe that switching doubled the odds. Then I got to reading the comments on the second post and somewhere in the 101 of them that there, are I became a believer.

If you remain unconvinced that B is the right answer, go read for your self – A Brilliant Reader Question.

If you are a smarty pants know-it-all, what the heck are you doing here reading my blog?