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A couple has two children, one of whom is a girl.

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Re: A couple has two children, one of whom is a girl.  [#permalink]

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New post 23 Apr 2016, 09:56
HKD1710 wrote:
Thanks Abhishek009,

I went thru all those solutions and i still did not understand only the following:

Quote:
WHY do we consider BG, GB as two cases instead of ONE case only. We are not arranging here.


I hope its clear with you now, in case of any doubt , please feel free to revert ( Because I know P&C and Prob Concepts are very confusing) !!

Happy Preparations

Abhishek
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Re: A couple has two children, one of whom is a girl.  [#permalink]

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New post 23 Apr 2016, 10:07
Abhishek009 wrote:
HKD1710 wrote:
Thanks Abhishek009,

I went thru all those solutions and i still did not understand only the following:

Quote:
WHY do we consider BG, GB as two cases instead of ONE case only. We are not arranging here.


I hope its clear with you now, in case of any doubt , please feel free to revert ( Because I know P&C and Prob Concepts are very confusing) !!

Happy Preparations

Abhishek


Any explanation on that specific part i mentioned would bring clarity. :)
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Re: A couple has two children, one of whom is a girl.  [#permalink]

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New post 23 Apr 2016, 10:25
HKD1710 wrote:
WHY do we consider BG, GB as two cases instead of ONE case only. We are not arranging here.


BG = Boy takes birth Before Girl

GB = Girl takes birth before Boy

PS: I know I might be contradicting my own theory of twins , but it is crucial to understand it this way. Even twins born on the same day may be few minutes apart


Does it help you anyway ?
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Re: A couple has two children, one of whom is a girl.  [#permalink]

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New post 23 Apr 2016, 10:38
2
HKD1710 wrote:

Any explanation on that specific part i mentioned would bring clarity. :)


Hi,
Do not get into kids as B or G,try with another example
say there are two different flavours of icecream - V and C..
50% chances that one can pick either and eat..
we know he ate two and one was surely a V.. what is the probabilty that he had two vanillas, V..
he could have had VC or CV or VV
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Re: A couple has two children, one of whom is a girl.  [#permalink]

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New post 23 Apr 2016, 10:42
1
Abhishek009 wrote:
HKD1710 wrote:
WHY do we consider BG, GB as two cases instead of ONE case only. We are not arranging here.


BG = Boy takes birth Before Girl

GB = Girl takes birth before Boy

PS: I know I might be contradicting my own theory of twins , but it is crucial to understand it this way. Even twins born on the same day may be few minutes apart


Does it help you anyway ?


well neither we need to apply the twin or age or any other theory. lets put it this way:

I am told that my neighbour has two child. one is girl another may be boy or girl. I went to my neighbour's house. here are the total case:

1. a boy opens the door (then other child as we already know is girl) hence - BG.
2. a girl opens the door. (then other child could be boy or girl )- hence (GB or GG)

This is why we have these three cases.

GG is favorable out of three. so 1/3.
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Re: A couple has two children, one of whom is a girl.  [#permalink]

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New post 23 Apr 2016, 10:44
chetan2u wrote:
HKD1710 wrote:

Any explanation on that specific part i mentioned would bring clarity. :)


Hi,
Do not get into kids as B or G,try with another example
say there are two different flavours of icecream - V and C..
50% chances that one can pick either and eat..
we know he ate two and one was surely a V.. what is the probabilty that he had two vanillas, V..
he could have had VC or CV or VV


Thanks chetan. Your assistance helps! Kudos :)
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Re: A couple has two children, one of whom is a girl.  [#permalink]

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New post 08 Sep 2017, 18:36
TimeTraveller wrote:
Sample space = {bb,bg,gb,gg}

Favourable event = {gg}.

Since it's given that one of the child is a girl, the new Sample Space = {bg,gb,gg}.

So, probability = 1/3. Ans (C).


Hi Bunuel,
If we consider above method, does it mean that the given probability of either boy or girl being 50% is not required to solve the problem?
And also can you please tell, the given probability translate into which of the below equations?:-
P(B U G)= 0.5
or
P(B) = P(G)= 0.5

*U = Union
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Re: A couple has two children, one of whom is a girl.  [#permalink]

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New post 30 Dec 2017, 00:05
AmoyV wrote:
A couple has two children, one of whom is a girl. If the probability of having a girl or a boy is 50%, what is the probability that the couple has two daughters?

A. 1/8
B. 1/4
C. 1/3
D. 1/2
E. 2/3


VERITAS PREP OFFICIAL SOLUTION:

While every bone in your body wants to say 1/2, that is not correct! This is tricky conditional probability and considering the different possibilities is the best way to get it correct. If the couple has 2 children then there are 4 possibilities: BB, BG, GB, GG.

If one of the children is a girl then only 3 possibilities remain: BG, GB, GG. Of those 3, only one is favorable to create 2 daughters (GG) so the answer is 1/3. Answer is (C )
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Re: A couple has two children, one of whom is a girl.  [#permalink]

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New post 12 May 2018, 03:59
OFFICIAL SOLUTION
Solution: While every bone in your body wants to say 1/2, that is not correct! This is tricky conditional probability and considering the different possibilities is the best way to get it correct. If the couple has 2 children then there are 4 possibilities: BB, BG, GB, GG.
If one of the children is a girl then only 3 possibilities remain: BG, GB, GG. Of those 3, only one is favorable to create 2 daughters (GG) so the answer is 1/3. Answer is (C )
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Re: A couple has two children, one of whom is a girl.  [#permalink]

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New post 21 Sep 2018, 03:47
REDWASP2205 wrote:
chetan2u

But knowing One of them is a girl, shouldn't we remove BG from the possible cases.

As the order isn't given here, we can't remove BG form the same set. All we may remove is BB, Boy and a Boy as this is an irrelevant answer option for us here.
As we already know that one of the Child is girl.
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Re: A couple has two children, one of whom is a girl.  [#permalink]

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New post 21 Sep 2018, 04:52
Bunuel --- Need your help to shine some more light on this, if possible. (I know this post is very old)

How can we use the probability approach in this question?
I understand that one of the children is already a girl. The probability that the other child is a girl is 1/2.
How does that line of reasoning completely fail here?

Thanks in advance. I am trying to understand the probability approach better here but am failing.
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Re: A couple has two children, one of whom is a girl. &nbs [#permalink] 21 Sep 2018, 04:52

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