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Two kids, with a nod to Teanchi and Beanchi


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20 replies to this topic

#1 bonanova

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Posted 16 July 2012 - 07:38 AM

Ned, Red, Ted and Zed are identical quadruplets alike in every way except one: the way that they describe the children in families that have two children. 

1. Ned says one is a boy, if that is a true statement; otherwise he says one is a girl.
2. Red says one is a girl, if that is a true statement; otherwise he says one is a boy.
3. If the older child is a boy, Ted says one is a boy; otherwise he says one is a girl.
4. Zed flips a coin and considers the taller (heads) or shorter (tails) child.
If the coin-selected child is a boy, he says one is a boy; otherwise he mentions the sex of the other child.

One of the four men, we don't know which, then tells us:

"Ok, so Teanchi and Beanchi are a married couple (dont ask me whose he and whose she)!  
They have two kids, one of them is a girl."

What is the probability that the other child is a girl? :)
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#2 bhramarraj

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Posted 16 July 2012 - 09:23 AM

Spoiler for

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#3 CaptainEd

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Posted 16 July 2012 - 03:34 PM

Spoiler for Good chance...

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#4 Molly Mae

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Posted 16 July 2012 - 03:38 PM

1. Ned says one is a boy, if that is a true statement; otherwise he says one is a girl.


Spoiler for


Spoiler for ...

Edited by Molly Mae, 16 July 2012 - 03:39 PM.

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A recipe for honey-pickled apples


Awards:

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Spoiler for Molly's Rules to Live By

#5 psykomakia

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Posted 16 July 2012 - 04:27 PM

Ned says one is a boy, if that is a true statement; otherwise he says one is a girl.


Does this mean that he will say "One is a boy" if and only if there is one boy and one girl, or also if there is one boy and another boy?
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#6 bonanova

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Posted 16 July 2012 - 04:34 PM

Does this mean that he will say "One is a boy" if and only if there is one boy and one girl, or also if there is one boy and another boy?


If either is a boy.
For our purposes, "One is a boy" and "At least one is a boy" are equivalent statements.
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The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
- Bertrand Russell

#7 Yoruichi-san

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Posted 16 July 2012 - 07:41 PM

Spoiler for Error


Spoiler for My solution


Edit: Bah, formatting...why does it ignore my spacing, etc after I click okay in the spoiler screen?

Edited by Yoruichi-san, 16 July 2012 - 07:50 PM.

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Women are definitely stronger. We are [Fe]males, after all...

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#8 bushindo

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Posted 16 July 2012 - 08:07 PM

Thought I had a question, but it turned out to be unnecessary. Agree with Yoruichi-San on the answer. Nice puzzle!
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#9 CaptainEd

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Posted 16 July 2012 - 09:05 PM

Durn, bit by Bayes again...
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#10 bonanova

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Posted 17 July 2012 - 01:31 AM

The OP intended to deny bias among reporters, since each can comment on any two-child family,
Even tho some statements are denied to some reporters for some families.

However ...

The greater intent of this puzzle was to cool the debate somewhat, housed in the Teanchi-Beanchi thread.

We don't know the algorithm used by the reporter, and now we understand that it matters.
Most of us "1/3" zealots assume the reporter was like Red.
But there is no basis for that [or any other] assumption.

Spoiler for my answer

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The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
- Bertrand Russell




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