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Published by Simon 08-13-2007
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This is reminiscent of similar dice riddles, but the answer to this one appears to defy logic. Unless I'm mistaken, this is not as obvious as it looks.

There are six unloaded die.
Each has been rolled out of your sight and hidden behind a cup.
You are informed that no more than one of them landed a 6 - but it may be that none of them did.

You are going to remove the cups one at a time.

Before you do, you label each cup with letters A to F. This designates the order in which you will remove them. You have complete discretion which cup is assigned each letter, but once labeled they must be removed in alphabetical sequence.

Having labelled them, it is time to remove the cups accordingly from A to F.

If one of the dice landed as 6, under which cup is it most likely to be found?
  #1 (permalink)  
By freeztar on 08-13-2007
Re: The Six Dice Puzzle

None of them, the dice are behind the cup.
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  #2 (permalink)  
By Simon on 08-13-2007
Re: The Six Dice Puzzle

It not that kind of a riddle!
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  #3 (permalink)  
By Kutan on 08-13-2007
Re: The Six Dice Puzzle

None of them..? The way it's worded is a little weird to me but I figure if you don't even know what numbers were rolled, they all have an equal chance of having a 6?
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  #4 (permalink)  
By Simon on 08-13-2007
Re: The Six Dice Puzzle

Quote:
Originally Posted by Kutan View Post
None of them..? The way it's worded is a little weird to me but I figure if you don't even know what numbers were rolled, they all have an equal chance of having a 6?
That is the intuitive answer. But is it correct?
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  #5 (permalink)  
By Jay-qu on 08-13-2007
Re: The Six Dice Puzzle

I would say so..
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  #6 (permalink)  
By sanctus on 08-13-2007
Re: The Six Dice Puzzle

I don't think it is correct, every time you lift a cup and it is not a 6 you have a higher probability of having a six...but to do the probability calculus you need to what is the probability of having a six in the first place (which is less than 1/6 since you know that 1 or zero dice are six (while to have the probability of 1/6 you would need to know that 1 dice is 6), hence there is a probability given in advance...).
For example if we have the probability of 75% to have one six then:
cupA: p(6|A)=prob(A)prob(throw 6)prob(external75%)=1/6*1/6*3/4
cupB: p(6|B)=1/5*1/6*3/4, since now only five ways to choose the order of cups
...
cupF: p(6|F)=1*1/6*3/4
-->hence it seems to me that in F it should be the most probable one. Now, if I understood wrong and you meant that there is the probability of 1/6 any dice gives 6, than they same argument holds without the term 3/4=75%...

Just note, I don't know if this is correct, but I think it is the way to think.
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  #7 (permalink)  
By eric l on 08-14-2007
Re: The Six Dice Puzzle

My guess :
The chances of finding a six are the same for each of the dice.
The chances that you have NO six at the first dice are 5/6
The chances that you have NO six by the time you reach the 6th dice are (5/6)^6 or 15625/466656
So, the chances that you do have a 6 by that time are 1 - this or 31031/46656 or about 2 out of 3. This would mean 2 of of 18 or 1/9 per dice.
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  #8 (permalink)  
By ronthepon on 08-14-2007
Re: The Six Dice Puzzle

Quote:
Originally Posted by Simon View Post
If one of the dice landed as 6, under which cup is it most likely to be found?
Assuming that one of the dice has indeed landed as a six, we are free to label the cups in whatever order we want.

So the probability of the 6 cup getting anything from A to F will probably be equal.
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  #9 (permalink)  
By sanctus on 08-14-2007
Re: The Six Dice Puzzle

Quote:
Originally Posted by ronthepon View Post
Assuming that one of the dice has indeed landed as a six, we are free to label the cups in whatever order we want.

So the probability of the 6 cup getting anything from A to F will probably be equal.
I don't agree, just imagine in the first cup there is no 6 but you know there is one hence the probability increases. The easiest way to see this is by supposing that you do the experiment and the first 5 cups have something different from 6, hence the last cup has a probability of 1 having a six.
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