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Probability and two groups

  1. Dec 6, 2006 #1
    Hi, I'd appriciate help with this problem;

    Person X and Y have equal number of kids. There are 3 movie tickets. The probability that 2 tickets go to kids of one and 1 ticket goes to the kids of other is 6/7. How many kids do X and Y have?

  2. jcsd
  3. Dec 6, 2006 #2


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    Supposing each way of distributing the tickets is of equal probability, you can find and expression using combinatorics for the desired probability in terms of N (the number of kids). Then set the probability equal to 6/7 and solve for N.
  4. Dec 7, 2006 #3
    sorry, but i don't see any connection between the data given and no. of kids, except that both have 2 or more kids. Could u please be more definite.
    Thanx for ur help.
  5. Dec 7, 2006 #4
    Let X have N children, and Y have N children. For starters, how many ways are there to distribute the 3 tickets among the 2N children?
  6. Dec 8, 2006 #5
    Well, i used Baye's theorem n i'm getting the no. of children to be 4, which is correct, thank You for your help.
  7. Dec 20, 2006 #6


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    Baye's theorem is not reqiured:
    2(nC2)(nC1)/(2nC3)=6/7 . Solving we get, n=4.
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