Quick Logic Problem

[Battleborne]

Oh great another genius post from Battleborne is en route.

Jealousy is one of the 7 deadly sins...CupCake...!!!!!!

 

[Epicurus]

Not because it's been established that each already has one boy. So we're calculating the probability only that the second child of each is a boy. The knowledge that each already has one boy is actually irrelevant and is one of those nasty little tricks that such questions often include just to mess with you.

That's what I was thinking but if you are calculating only their 2nd child shouldn't you be right with 25%?

What are we missing?

 

[Thorn]

That's what I was thinking but if you are calculating only their 2nd child shouldn't you be right with 25%?

What are we missing?

Yes I am right; Dano acknowledged that.

 

[KingCondanomation]

Okay give me a hint, because I have just finished doing 8 million problems like these for the LSAT and I am absolutely lost on this.

Hint: With a pair of dice at the craps table, why are you more likely to roll an eleven than the numerical equivalent of a dozen?

 

[Thorn]

Hint: With a pair of dice at the craps table, why are you more likely to roll an eleven than the numerical equivalent of a dozen?

There is only one way you can roll a 12; there are two possible ways to roll eleven (5 + 6 or 6 + 5).

 

[KingCondanomation]

Yes I am right; Dano acknowledged that.

Just to be clear, all I acknowledged was that .5 X .5 = .25 or 25% is correct math.
But 25% is still the wrong answer to the problem.

 

[Cancel 2016.2]

so you have the possibility of

boy boy, boy girl, girl boy, girl girl

Still not seeing how this isn't 25%.

 

[KingCondanomation]

There is only one way you can roll a 12; there are two possible ways to roll eleven (5 + 6 or 6 + 5).

Correct. Now apply the same logic to one of the women.

 

[KingCondanomation]

so you have the possibility of

boy boy, boy girl, girl boy, girl girl

Still not seeing how this isn't 25%.

Another hint: There can never be a girl-girl for either of the women as both have at least one son.

 

[Bonestorm]

so you have the possibility of

boy boy, boy girl, girl boy, girl girl

Still not seeing how this isn't 25%.

There is no possibility of girl-girl. That's the rub. I think.

 

[Cancel 2016.2]

Another hint: There can never be a girl-girl for either of the women as both have at least one son.

Dano... yes, you can add a boy-boy to each of those scenarios, the fact that they each have a son already doesn't change the results of the unknown child.

you would have

boy boy with boy girl
boy girl with boy boy
boy boy with boy boy
boy girl with boy girl

 

[Cancel3]

Then its 12.5%

 

[Cancel 2016.2]

There is no possibility of girl-girl. That's the rub. I think.

I was posting the scenarios for the second child only... the fact that they each already have a boy is a known quantity. But for Danos sake I clarified this.

 

[KingCondanomation]

Then its 12.5%

No

 

[KingCondanomation]

Dano... yes, you can add a boy-boy to each of those scenarios, the fact that they each have a son already doesn't change the results of the unknown child.

you would have

boy boy with boy girl
boy girl with boy boy
boy boy with boy boy
boy girl with boy girl

You are getting closer.
Another hint: You have listed 4 possibilities above, there are more than that.

 

[Battleborne]

Not rocket science..ya want a boy wear briefs ya want a girl wear boxers..a proven temperature oxymoron from science...

 

[Bonestorm]

You are getting closer.
Another hint: You have listed 4 possibilities above, there are more than that.

Is there a hermaphroditic curve ball you aren't disclosing?

 

[Cancel 2016.2]

You are getting closer.
Another hint: You have listed 4 possibilities above, there are more than that.

No, there are not. Unless you are going to suddenly tell us that one of the children in question is the step child of Jane and birth child of Joan.

The boy portion on one child for each is fixed. Each has one. So each of the other probabilities is listed.

 

[KingCondanomation]

Is there a hermaphroditic curve ball you aren't disclosing?

LOL, no. No extra info is needed than what was originally given to deduce the right answer.

 

[Thorn]

You are getting closer.
Another hint: You have listed 4 possibilities above, there are more than that.

Actually, we can eliminate the first child's gender from consideration as that has been established.

So the possibilities remain (including both mothers):

Boy - boy
Boy - girl (or Girl - boy; the order doesn't matter)
Girl - girl

Darnit, the answer really is 33%!