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combinations and permutions query

  • 03-05-2014 8:19pm
    #1
    paintitblack
    Registered Users, Registered Users 2 Posts: 88 ✭✭


    Hi
    2 Quick queries, if there are 11small clients, 9 medium clients and 6 large and if a random sample of 6 is taken and there must be equal numbers each. Is the method of doing this 11c2 + 9c2 + 6c2??
    And secondly if at most 1 large client is selected is the method 21c6??


Comments

  • #2
    Blackpanther95
    Registered Users, Registered Users 2 Posts: 176 ✭✭Blackpanther95


    Multiply don't add.


  • #3
    Blackpanther95
    Registered Users, Registered Users 2 Posts: 176 ✭✭Blackpanther95


    The second one is 20c5 * 11c1 + 20c6. I.e either take 1 large client: so we have 11c1 and chose the five rest so 20c5. Or chose no large clients: so we chose 6 small or medium 20c6. We add because we said OR, we multiply when we say AND (not technical obviously)


  • #4
    paintitblack
    Registered Users, Registered Users 2 Posts: 88 ✭✭paintitblack


    Very helpful thank you


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