Omnimaga
General Discussion => Other Discussions => Miscellaneous => Topic started by: Builderboy on September 27, 2011, 07:57:23 pm

I have two coins in my hand. I flip both of them secretly until I get a result that is not two tails. I then turn to you and show you that one of the coins is heads, and ask what the probability of the other being heads.


Indeed :] Most people take the intuitive result, which is wrong in this case, which is why I like this puzzle so much ^^

I actually know the answer because of the Monty Hall Problem with Marilyn Vos Savant.

Ah yes! I just now realized the problems are equivalent! I actually derived this from a separate problem about two children, but now i see how similar it is to the monty hall problem ^^

I think I understand how this works, would you mind explaining step by step?

Okay, there are three possible arrangements for the coins, given that it's not two tails: HH, TH, HT
since one of them is heads, the other can be a hh, th, or ht. The probability where the remaining letter is a heads is one out of three.

Oh, I get it, because it would be a two thirds chance that the other coin is tails.

That's not intuitive at all ... whoa :o