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Probability of getting two boys question

  1. Oct 30, 2009 #1
    in a family with 2 children , what is the possibility that there will be 2 boys if we know that at least one is a boy,

    the correct answer is 0.33 but how do i get it,


    the way i see it we have 4 options
    boy girl
    girl boy
    boy boy
    girl girl

    therefore only one is a boy- boy option, therefore p=0.25
     
  2. jcsd
  3. Oct 30, 2009 #2
    i see my problem, the options are
    boy girl
    girl boy
    boy boy

    so it really is 1/3, but how do i get this using equations

    using P(X/Y) etc
     
  4. Oct 30, 2009 #3

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    What you have done is a perfectly valid method and far easier than "using equations".
     
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