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One Girl - One Boy

Best Answer Riddari , 13 July 2007 - 07:38 PM

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348 replies to this topic

#1 skale

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Posted 12 July 2007 - 05:03 PM

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 kid is also a girl.

Assume safely that the porbability of each gender is 1/2.

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#2 mdsl

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Posted 12 July 2007 - 05:48 PM

It's a lousy puzzle.
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#3 unreality

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Posted 12 July 2007 - 07:41 PM

its 1/2, so its a lousy puzzle...

lol but the title says "One Girl - One Boy" so maybe there's a 0% chance the second kid is a girl because its a boy?
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#4 skale

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Posted 12 July 2007 - 10:18 PM

It's a lousy puzzle.

Its not, wait for the reasoning till someone gets the right answer!
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#5 savagegamer90

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Posted 12 July 2007 - 10:44 PM

are these people or animals, because you never said child
you said kid, which can refer to a goat
and you just said married couple
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#6 skale

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Posted 12 July 2007 - 11:12 PM

are these people or animals, because you never said child
you said kid, which can refer to a goat
and you just said married couple

Yes, we are talking about human-beings here, this is no lateral thinking puzzle.

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Good job rookie, these spoiler tabs are excellent!
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#7 savagegamer90

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Posted 12 July 2007 - 11:18 PM

the other child has to be a boy,
first you have one girl then the next needs to be a guy
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#8 savagegamer90

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Posted 12 July 2007 - 11:20 PM

oops i forgot
probability is 1/2
or 1 out of 2
they have 2 children
1 out of two is a girl then the other 1 out of two has to be a boy
(edit: I suck at spelling so I fixed it)
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#9 skale

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Posted 12 July 2007 - 11:27 PM

oops i forgot
probability is 1/2
or 1 out of 2
they have 2 children
1 out of two is a girl then the other 1 out of two has to be a boy
(edit: I suck at spelling so I fixed it)

The probability of having a girl or a boy is same and is 1/2. i.e. same as saying if a fair coin is tossed then odds of getting a head is 50% and getting a tail is also 50%. Hope this makes is more clear, take another digg @ the question!
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#10 imtcb

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Posted 13 July 2007 - 05:38 AM

The answer is 25%. Before they had children the probability for a girl first is 50%. The probability for a girl second is 50%. BUT, to have 2 girls the probability moves to half of half, or 25%.

Comparing a coin toss is a common mislead. A single coin toss is of course 50/50. But 2 consecutive tosses is 50/50 for the first, and 25/75 for the second. Taken as a set (as you must in a family), you cannot discount the total probability by looking at the single toss.

Much like this:
I have 3 boxes (a - b - c).
2 have nothing in them.
1 has a million dollars.
If you guess the correct one, you get the money.

You pick one.
Out of the remaining 2, I show you that one is of course empty.