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Math Help - permutation - basic

  1. #1
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    permutation - basic

    below the basic question of permutation:

    given that 4 letters are chosen from the word PAYMENT,find the number of arrangement that start with a vowel

    ans: 2P1 x 6P3 = 240
    my ans: 120

    any guide?
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  2. #2
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    It seems like the question assumes the only vowel can be in the first postition.

    Giving ^2P_1 \times ^6P_3 = 240


    As you may realise you start the 4 letter arrangement with a vowel and have another vowel (as there are 2) in positions 2-4.
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  3. #3
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    tq for your post, but i hope u can commnet my ans attached as below:

    http://img839.imageshack.us/img839/7452/99010889.jpg
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  4. #4
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    Why can't N or T be in the last postition? I think you are calculating combinations not permutations as you should. Are you aware of the difference?
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  5. #5
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    it mean what i am doing is combination?
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  6. #6
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    Hello, nikk!

    Why do they include Y in these problems?
    There is always that controversy: "Is Y a vowel?"


    Given that 4 letters are chosen from the word PAYMENT,
    find the number of arrangement that start with a vowel.

    If Y is a vowel: . \;\underbrace{\text{vowel}}_3 \text{ - } \underbrace{\text{any}}_6 \text{ - } \underbrace{\text{any}}_5 \text{ - }\underbrace{\text{any}}_4 \;=\;360


    If Y is not a vowel: . \;\underbrace{\text{vowel}}_2 \text{ - } \underbrace{\text{any}}_6 \text{ - } \underbrace{\text{any}}_5 \text{ - }\underbrace{\text{any}}_4 \;=\;240

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  7. #7
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    tq ror your idea..nice
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