Simple problem
September 15th, 2010 at 3:44:14 PM
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Assumptions- 1. boys and girls are born with equal frequency.
2. No identical twins
Question-
I have 2 children. One is a boy. What is the chance that the other one is a boy?
After most say 50% I will propose a different answer and await the analysis.
Thanks all.
2. No identical twins
Question-
I have 2 children. One is a boy. What is the chance that the other one is a boy?
After most say 50% I will propose a different answer and await the analysis.
Thanks all.
September 15th, 2010 at 3:47:53 PM
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1 / 3
Wisdom is the quality that keeps you out of situations where you would otherwise need it
September 15th, 2010 at 3:50:27 PM
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Quote:After most say 50% I will propose a different answer and await the analysis.
I'll beat you to it, by proposing an answer of 1/3 :)
Edit: Oops. Looks like I got beaten myself :)
"When two people always agree one of them is unnecessary"
September 15th, 2010 at 3:54:55 PM
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Nevermind, think I messed up here.
edit2: I mean, I've heard this one before so was thinking 1/3 was right, but when I did the math I came up with 2/3.
edit3: Oh, I see where I was wrong. It is 1/3. There are four possibilities from two birthings with 50% likeliness to go either way, so you can have a Boy then Boy, Girl then Girl, Boy then Girl and Girl then Boy. If we know one is a boy we know it is not Girl then Girl. So, there are three remaining possibilities, and only one has two boys. 1/3.
edit2: I mean, I've heard this one before so was thinking 1/3 was right, but when I did the math I came up with 2/3.
edit3: Oh, I see where I was wrong. It is 1/3. There are four possibilities from two birthings with 50% likeliness to go either way, so you can have a Boy then Boy, Girl then Girl, Boy then Girl and Girl then Boy. If we know one is a boy we know it is not Girl then Girl. So, there are three remaining possibilities, and only one has two boys. 1/3.
Solo venimos, solo nos vamos. Y aqui nos juntamos, juntos que estamos.
September 15th, 2010 at 4:28:44 PM
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Thanks all. When i try to explain the 1/3 answer it is often scoffed at. But I can't get it past the W of V crew. Which is good.....
September 16th, 2010 at 4:34:11 AM
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Similar problem in terms of dice:
I roll two fair 6-sided dice. I tell you one of them is a 2. What are the odds the other die shows a 2 as well?
I roll two fair 6-sided dice. I tell you one of them is a 2. What are the odds the other die shows a 2 as well?
-Dween!
September 16th, 2010 at 7:41:36 AM
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wow
well you would have got me, but now I get it. The unsuspecting mind wants to incorrectly change the scenario into "the first child was a boy, so what are the odds the second will be a boy?" This reformed question actually seems to be conditional, but isnt and can lead into gambler's fallacy! So as I was patting myself on the back for realizing that ...
All very interesting and I am easily duped, perhaps one day I'll get better.
well you would have got me, but now I get it. The unsuspecting mind wants to incorrectly change the scenario into "the first child was a boy, so what are the odds the second will be a boy?" This reformed question actually seems to be conditional, but isnt and can lead into gambler's fallacy! So as I was patting myself on the back for realizing that ...
All very interesting and I am easily duped, perhaps one day I'll get better.
the next time Dame Fortune toys with your heart, your soul and your wallet, raise your glass and praise her thus: Thanks for nothing, you cold-hearted, evil, damnable, nefarious, low-life, malicious monster from Hell! She is, after all, stone deaf. ... Arnold Snyder
September 16th, 2010 at 7:56:24 AM
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Wow.Quote: DweenSimilar problem in terms of dice:
I roll two fair 6-sided dice. I tell you one of them is a 2. What are the odds the other die shows a 2 as well?
The same knee-jerk reaction that would cause an answer of 50% chance of a second son, would say a 1/6 chance of a second two.
But since there are 11 combinations with AT LEAST one die showing a two, and only one of them showing a pair of twos, then the answer is 1/11.
Using that logic, it would seem that if told that one of them is NOT a two, the odds that the other IS a two would be 10/36.
Is that really right? It seems so counter-intuitive!
I invented a few casino games. Info:
http://www.DaveMillerGaming.com/
Superstitions are silly, childish, irrational rituals, born out of fear of the unknown. But how much does it cost to knock on wood? 😁
September 16th, 2010 at 8:03:11 AM
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Man, this is cool stuff.
If told that the oldest child was a son, and asked what the chance that the other child is also a son, then it reverts back to 50%
Similarly, if a red and green die were thrown, and you're told that the red die shows a two, then the odds that the green die is a two reverts back to 1/6.
You pick up the extra combinations when you don't know which is which.
If told that the oldest child was a son, and asked what the chance that the other child is also a son, then it reverts back to 50%
Similarly, if a red and green die were thrown, and you're told that the red die shows a two, then the odds that the green die is a two reverts back to 1/6.
You pick up the extra combinations when you don't know which is which.
I invented a few casino games. Info:
http://www.DaveMillerGaming.com/
Superstitions are silly, childish, irrational rituals, born out of fear of the unknown. But how much does it cost to knock on wood? 😁
September 16th, 2010 at 9:33:16 AM
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Quote: DJTeddyBearWow.
But since there are 11 combinations with AT LEAST one die showing a two, and only one of them showing a pair of twos, then the answer is 1/11.
That is correct.
Quote: DJTeddyBearUsing that logic, it would seem that if told that one of them is NOT a two, the odds that the other IS a two would be 10/36.
Hmm... right idea, but I think it would be 10/35, or 2/7. You can eliminate the double 2's at the first step, then take the all combinations with a single two as above. I had never heard the problem turned on its head like that, and it makes for an interesting question!
Reminds me of the riddle: You have 2 normal American coins in your pocket that total 30 cents. One of them is not a nickel (5 cents). What are the two coins? Answer: A quarter (25 cents) and a nickel (5 cents). The quarter is the one that's not a nickel.
-Dween!
September 16th, 2010 at 12:19:22 PM
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Quote: SOOPOOAssumptions- 1. boys and girls are born with equal frequency.
2. No identical twins
Question-
I have 2 children. One is a boy. What is the chance that the other one is a boy?
After most say 50% I will propose a different answer and await the analysis.
Thanks all.
50% Older sister, younger sister, older brother, or younger brother, all equally likely, correct?
September 17th, 2010 at 10:22:49 PM
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Sorry, it was here, then gone. I didn't post here. Ken
September 18th, 2010 at 6:46:31 AM
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For what purpose? Your post has NOTHING to do with anything in this thread, but EVERYTHING to do with why you're disliked around here.Quote: mrjjjI'm making one (copy/paste) statement so I dont have to re-do it on the other 7 boards...
I invented a few casino games. Info:
http://www.DaveMillerGaming.com/
Superstitions are silly, childish, irrational rituals, born out of fear of the unknown. But how much does it cost to knock on wood? 😁
September 20th, 2010 at 2:50:12 AM
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Your initial question is not really a trick question. Had you asked how many possible combinations of two siblings there could be, most would answer correctly. had you asked how many, given one was a predetermination, some would get it it wrong 'cause there math ends there..
What is the chance of the other one being a boy?
50/50.
Unless your in china
Stimulating riddle all the same
thanks
What is the chance of the other one being a boy?
50/50.
Unless your in china
Stimulating riddle all the same
thanks
