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Easy probability Question O.L.. Please?

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Comments

  • #32
    finality
    Registered Users, Registered Users 2 Posts: 1,763 ✭✭✭finality


    It's definitely not on the OL course, I noticed that in one of the SEC circular letters. So no need to worry about this guys :)


  • #33
    Namlub
    Closed Accounts Posts: 6,298 ✭✭✭Namlub


    If it's seriously not on the course I don't know why I'm even bothering with sample papers because they obviously don't correspond to the syllabus, ugh.


  • #34
    whiteandlight
    Closed Accounts Posts: 2,359 ✭✭✭whiteandlight


    Which circular was that? You all seem to mixing up permutations and combinations. Permutations are on the HL course and not the ordinary but combinations are on both.

    Combinations are ways of choosing r objects from n objects when you don't care about order eg when downloading songs, it doesn't matter which you download first.

    Permutations are ways of choosing r objects from n objects when order matters eg when choosing first, second and third place in a competition.

    Only combinations are on OL and you can do them using the nCr function on your calculator.

    Eg how many committees of three can be chosen from seven people?
    7ncr3

    If one of the seven members John can not be chosen, how many committees are possible?
    There are only 6 people left to chose from but we still need three
    6ncr3

    If Mary has to be on the committee how many possible arrangements are there?
    Mary is chosen leaving 6 people to pick from but we already have one of the three positions filled so we only need two more
    6ncr2


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