1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Dice question

  1. Feb 13, 2012 #1
    1. The problem statement, all variables and given/known data

    If someone could just check my work, thanks!
    If five dice are rolled once each, what is the probability of rolling exactly 4 identical numbers?


    2. Relevant equations



    3. The attempt at a solution

    This is what I have:
    (1)(1/6)(1/6)(1/6)(5/6)=5/1296
     
  2. jcsd
  3. Feb 13, 2012 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    That's the probability of doing it in a specific way. Say, first four identical, last one not identical. The problem doesn't specify any particular way.
     
  4. Feb 13, 2012 #3
    Ok, so would it be this instead?
    (6)(1/6)3(5/6)
     
  5. Feb 13, 2012 #4

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    No. Why '6'? How many ways are there to choose the four identical dice out of five dice?
     
  6. Feb 13, 2012 #5
    i'm not sure, this is one of my study guide questions and this is why i'm asking...
     
  7. Feb 13, 2012 #6

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Last edited: Feb 13, 2012
  8. Feb 14, 2012 #7
    I took a break from this problem but here is my newest attempt:
    choose(5,4) = 5
    so is it... 5(1/6)3(5/6)?
     
  9. Feb 14, 2012 #8

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Well, yes. Doesn't that seem more right to you than the first try?
     
  10. Feb 14, 2012 #9

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    I think your basic approach is risky: you need to develop the answer step-by-careful step, rather than flailing around and writing down some almost random answers. If you need to keep asking "Am I right"?..."OK, what about now?..." it indicates that you are not at all confident about what you are doing. You would likely be more confident if you were more systematic. Ask yourself the following: suppose the 4 identical numbers are all 1. What would be the probability of that (that is, of getting 4 1's and 2 non-1's)? Think about getting four 2's (instead of 4 1's), then four 3's, etc. Does it matter what the number is? Can you put this all together?

    RGV
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Dice question
  1. Throwing Dice (Replies: 2)

  2. Probability of a dice (Replies: 3)

Loading...