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Homework Help: What's wrong with this

  1. Nov 7, 2007 #1
    [SOLVED] what's wrong with this

    nPr= n!/(n-r)! and here in permutation order is important, and in combination
    nCr= n!/( r!(n-r)! ) order is not important, so the propability of ana event will be more for combination from permutation, but permutation is combination times r!, so what is wrong with me and not with my question:smile:
    Last edited: Nov 7, 2007
  2. jcsd
  3. Nov 7, 2007 #2
    i dont know who told u that in permutation order is not important because i think it is important...that's the difference between permutation and combination.
  4. Nov 7, 2007 #3
    sorry i was mistaken but now i corrected my question
  5. Nov 7, 2007 #4
    the PROBABILITY will be more for combination
    eg. nCr=7
    and nPr= 60
    so lets say the number 2 is in both then prob for nCr is 2/7
    and for nPr it's 2/60
    2/7 is greater than 2/60
    am i making any sense?
    i'm not sure if that's 100% right.
  6. Nov 7, 2007 #5
    i didn't understand you, i mean if n and r are the same for combination and permutation, the result will be nCr > nPr, that is what i'm not understanding, but what is r and n in your post?
  7. Nov 7, 2007 #6
    whatever r and n are...it doesnt matter because u want the probability, so if nPr>nCr, then the probaility of nCr is > prob of nPr.
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