Jeepster
Jeepster
Joined: Jul 7, 2013
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January 13th, 2014 at 8:11:22 PM permalink
As it seems to be the season for puzzles try this one.

You see me out with one of my two children, who happens to be a boy.
What's the chances of the other child at home also being a boy?

The only info you have and are allowed to know is-
I have exactly two children, the boy with me and another child at home.
Assume a world wide boy/girl birth ratio of 50/50.

It's not a trick question, there's no play on words or any other shenanigans involved.
A photon without any luggage checks into a hotel, he's travelling light.
rudeboyoi
rudeboyoi
Joined: Mar 28, 2010
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January 13th, 2014 at 8:28:12 PM permalink
25%. Can be BB GG BG GB. Only 1 out of 4 combos contain two boys.
beachbumbabs
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beachbumbabs
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January 13th, 2014 at 8:30:31 PM permalink
Quote: rudeboyoi

25%. Can be BB GG BG GB. Only 1 out of 4 combos contain two boys.



Can't be GG, because you know one is a boy for sure.
If the House lost every hand, they wouldn't deal the game.
Jeepster
Jeepster
Joined: Jul 7, 2013
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January 13th, 2014 at 8:31:57 PM permalink
Sorry Rudeboyio incorrect, you made a fundamental mistake concerning the info I gave you.
A photon without any luggage checks into a hotel, he's travelling light.
rudeboyoi
rudeboyoi
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January 13th, 2014 at 8:33:21 PM permalink
New answer :)

33%. Can be BB, BG, or GB. Only 1 out of 3 combos contains 2 boys.
24Bingo
24Bingo
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January 13th, 2014 at 8:52:31 PM permalink
rudeboyoi: Say it with me - "gambler's fallacy."

But...

I know there's a positive correlation between the sexes of a couple's children. I don't happen to know what it is, but the chance would be somewhere north of 50%.
The trick to poker is learning not to beat yourself up for your mistakes too much, and certainly not too little, but just the right amount.
Wizard
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Wizard
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January 13th, 2014 at 8:57:04 PM permalink
This is not the way this problem is usually worded but I think the answer you're looking for is...

1/3
It's not whether you win or lose; it's whether or not you had a good bet.
Jeepster
Jeepster
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January 13th, 2014 at 8:58:29 PM permalink
24Bingo, it would have to be a massive and unrealistic correlation to make the answer higher than 50%.
Anyways, any correlation can be ruled out for the purpose of this puzzle.
A photon without any luggage checks into a hotel, he's travelling light.
Jeepster
Jeepster
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January 13th, 2014 at 9:06:05 PM permalink
Well rudeboyoi as you rounded down your answer I'll have to give it to the Wizard for giving the first correct answer.
Sorry about that :)
A photon without any luggage checks into a hotel, he's travelling light.
24Bingo
24Bingo
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January 13th, 2014 at 9:13:11 PM permalink
Hold up, though. That's wrong.

Equal probabilities: BB, GG, BG, GB.

We eliminate GG for obvious reasons.

BUT... we eliminate GB also, because putting the child brought with you first is as good an ordering as any, it being the only thing we have to differentiate the two.

This isn't the Three Prisoner problem. You've given us no information.
The trick to poker is learning not to beat yourself up for your mistakes too much, and certainly not too little, but just the right amount.

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