## Poll

1 vote (1.72%) | |||

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14 votes (24.13%) | |||

39 votes (67.24%) | |||

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1 vote (1.72%) | |||

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1 vote (1.72%) | |||

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2 votes (3.44%) |

**58 members have voted**

I just couldn't let the last word be incorrect.

If black side can be observed, then it's 2/3.

If only white side can be observed, then it's 1/2.

Quote:sonuvabish

The coin is always white when you pull it out, 100% of the time. It is immaterial which white side comes out on the all-white coin because you are not observing 2 coins. That means there is a 50% the other side is white. Re-read the question. 2/3 is the probability that one of the remaining 3 faces is white; you either have the all-white coin, or you don't.

2/3 is simply the ratio of white faces to total unseen faces. This is the initial thought that everyone should have; everyone knows the chance of randomly selecting a white face, excluding the given, is 2/3--that was learned in elementary. If this is actually the correct answer, it is a trick question with poor wording. I would not call that controversial.

False. This is very similar to the Monty Hall problem (check wikipedia). Three closed doors - one has a car, the other two have nothing behind them. You point at one of the three doors. The host walks to the doors and opens one of the other two doors, and reveals that the car isn't behind that one. You can now choose to either keep your door or switch doors. What do you do? Open your door or open the other one? Straight from the movie 21! You can't ignore the information you're given.

Quote:RSThe question is worded poorly. I understand why one would say 2/3, but the question suggests the white side must be observed (and the black side cannot be observed).

Hahaha, what question are you reading?

Quote:Wizard

There are two coins in a bag. One is white on one side and black on the other. The other is white on both sides.

You randomly draw one coin, and observe one side only, which is white.

What is the probability the other side of that coin is white?

That sounds like you randomly draw one coin, and observe one side only, which happens to be white.