Tuesday 3 July 2012

Sunday Born Boy

Given are 2 children. What is the probability that both of them are boys given that one of them is a boy and is born on Sunday?

2 comments:

  1. The problem should be : probably that both are boys, else probability one of them is a boy given on is a boy =1.
    The answer to corrected problem is 13/27

    ReplyDelete
  2. For those who didn't get
    Try making a sample space
    1st child = {Boy, Girl}
    1st child born on {Sun,Mon,Tue,Wed,Thu,Fri,Sat}
    2nd child = {Boy, Girl}
    2nd child born on {Sun,Mon,Tue,Wed,Thu,Fri,Sat}

    with the constraint one being boy born on Sunday
    {(BSu,BSu),(BSu,BMo),(BSu,BTu),(BSu,BWe)(BSu,BTh)(BSu,BFr)(BSu,BSa)(BMo,BSu)(BTu,BSu)(BWe,BSu)(BTh,BSu)(BFr,BSu)(BSa,Bsu}
    Another 7 cases when 1st is boy and born on Sunday with 2nd as girl born on any 7 days
    Another 7 cases when 2nd is boy and born on Sunday with 1st as girl born on any 7 days

    Thus, Ans = 13/27

    ReplyDelete