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A bag contains two red beads and two green beads

  1. Jan 9, 2004 #1
    Need help...
    A bag contains two red beads and two green beads. You reach into the bag pull out a bead, replacing it with a red bead regardless of the color you pulled out. What is the probability that all beads in the bag are not red after three such replacements?
     
  2. jcsd
  3. Jan 10, 2004 #2

    uart

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    Hmmm, at a guess I'd say 71.875% :)
     
  4. Jan 10, 2004 #3
    I would think it is the probability of pulling out the two green beads in the first three replacement. So if my math is correct, it should be:

    (2/4 * 1/4 * 4/4) + (2/4 * 3/4 * 1/4) + (2/4 * 2/4 * 1/4)
     
  5. Jan 10, 2004 #4

    Hurkyl

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    You could draw a tree of all the possibilities.
     
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