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Counting problem

  1. Nov 20, 2013 #1
    Question 1:

    My question is how do I know when to use the permutation theorem or comination theorem?

    Theorem in paint document

    I'm asking because I would have used permutation thm. on 46 but I was wrong.


    Problem 46 b. and Problem 47 a. seem similar. The two main differences that I see are
    1. 46. We are given a group of ten people to choose from
    47. We are given a group of six people to choose from

    2. 46. Placement of bride and groom does not matter (Bride and groom must be in picture- No reference to placement)
    47. Placement of bride and groom matters (Bride must be next to groom)

    Therefore do I use combination if Placement matters?
    And permutation if placement does not matter?

    Question 2:
    How would the answer to 46 b change if bride must be next to groom?
    and
    how would answer to 47 a change if bride and groom must be in picture?
     

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  3. Nov 20, 2013 #2

    haruspex

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    I agree with you. The answer given to 46b is for choosing the 6 people, not for arranging them in a row.
    If you care to post your answers to 46a,b,c I (or someone) will check them.
     
  4. Nov 21, 2013 #3
    for number 47 part a. If i changed the problem to, the bride and groom must be in the picture then the answer would be,
    4 choose 4 = 1.
     
  5. Nov 21, 2013 #4

    haruspex

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    Did you mean 'must not be in the picture'?
     
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