App that counts probabilities in c++

  1. Hey,I am making an app that counts probabilities in c++(win32){for those who knows}.
    I have found three formulas of equation,but I need some help for one.

    For example we have a die,and we hit it 6 times.
    Can we count with an formula,the probabilities to have the number "5",three times exactly?(no less,no more)

    Thanks!!!
     
  2. jcsd
  3. mathman

    mathman 6,395
    Science Advisor
    Gold Member

    Use the binomial theorem.
    k out of n with probability p of success on one roll (q=1-p), is pkq(n-k)n!/{k!(n-k)!}.
    Your example: n = 6, k = 3, p = 1/6.
     
  4. Can you explain more because I hear about that first time?

    Or you could send me a tutorial??
     
  5. mathman

    mathman 6,395
    Science Advisor
    Gold Member

  6. Yea,I found an intersting site called "Math is fun",and I undestood it,but how I can count probabilities with that?
     
  7. Nugatory

    Staff: Mentor

    For the example in your original post:

    You cast the die six times, so there are ##6^6## equally likely sequences of results. Because they are equally likely, the probability of getting any given sequence is one in ##6^6##. How many of these sequences include exactly three fives?
     
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