Author 
Message 
TAGS:

Hide Tags

Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 3405
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)

Re: A couple has two children, one of whom is a girl. [#permalink]
Show Tags
23 Apr 2016, 10:56
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
_________________
Thanks and Regards
Abhishek....
PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS
How to use Search Function in GMAT Club  Rules for Posting in QA forum  Writing Mathematical Formulas Rules for Posting in VA forum  Request Expert's Reply ( VA Forum Only )



Moderator
Joined: 22 Jun 2014
Posts: 1034
Location: India
Concentration: General Management, Technology
GPA: 2.49
WE: Information Technology (Computer Software)

Re: A couple has two children, one of whom is a girl. [#permalink]
Show Tags
23 Apr 2016, 11:07
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 AbhishekAny explanation on that specific part i mentioned would bring clarity.
_________________
 Target  720740 http://gmatclub.com/forum/informationonnewgmatesrreportbeta221111.html http://gmatclub.com/forum/listofoneyearfulltimembaprograms222103.html



Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 3405
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)

Re: A couple has two children, one of whom is a girl. [#permalink]
Show Tags
23 Apr 2016, 11:25
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 ?
_________________
Thanks and Regards
Abhishek....
PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS
How to use Search Function in GMAT Club  Rules for Posting in QA forum  Writing Mathematical Formulas Rules for Posting in VA forum  Request Expert's Reply ( VA Forum Only )



Math Expert
Joined: 02 Aug 2009
Posts: 5777

Re: A couple has two children, one of whom is a girl. [#permalink]
Show Tags
23 Apr 2016, 11:38
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
_________________
Absolute modulus :http://gmatclub.com/forum/absolutemodulusabetterunderstanding210849.html#p1622372 Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
GMAT online Tutor



Moderator
Joined: 22 Jun 2014
Posts: 1034
Location: India
Concentration: General Management, Technology
GPA: 2.49
WE: Information Technology (Computer Software)

Re: A couple has two children, one of whom is a girl. [#permalink]
Show Tags
23 Apr 2016, 11:42
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.
_________________
 Target  720740 http://gmatclub.com/forum/informationonnewgmatesrreportbeta221111.html http://gmatclub.com/forum/listofoneyearfulltimembaprograms222103.html



Moderator
Joined: 22 Jun 2014
Posts: 1034
Location: India
Concentration: General Management, Technology
GPA: 2.49
WE: Information Technology (Computer Software)

Re: A couple has two children, one of whom is a girl. [#permalink]
Show Tags
23 Apr 2016, 11:44
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
_________________
 Target  720740 http://gmatclub.com/forum/informationonnewgmatesrreportbeta221111.html http://gmatclub.com/forum/listofoneyearfulltimembaprograms222103.html



Manager
Joined: 27 Jun 2015
Posts: 60
WE: Information Technology (Computer Software)

Re: A couple has two children, one of whom is a girl. [#permalink]
Show Tags
08 Sep 2017, 19:36
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



Math Expert
Joined: 02 Sep 2009
Posts: 44657

Re: A couple has two children, one of whom is a girl. [#permalink]
Show Tags
30 Dec 2017, 01:05
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 )
_________________
New to the Math Forum? Please read this: Ultimate GMAT Quantitative Megathread  All You Need for Quant  PLEASE READ AND FOLLOW: 12 Rules for Posting!!! Resources: GMAT Math Book  Triangles  Polygons  Coordinate Geometry  Factorials  Circles  Number Theory  Remainders; 8. Overlapping Sets  PDF of Math Book; 10. Remainders  GMAT Prep Software Analysis  SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS)  Tricky questions from previous years.
Collection of Questions: PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.
What are GMAT Club Tests? Extrahard Quant Tests with Brilliant Analytics




Re: A couple has two children, one of whom is a girl.
[#permalink]
30 Dec 2017, 01:05



Go to page
Previous
1 2
[ 28 posts ]



