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Math Help - Probability Theory

  1. #1
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    Probability Theory

    Hey guys I need some help with this problem-
    What is the probability of these events when we randomly select a permutation of {1,2,3,4}?
    c)4 precedes 1 and 4 precedes 2
    d)4 precedes 1, 4 precedes 2, 4 precedes 3
    e)4 precedes 3 and 2 precedes 1

    I got (a) and (b) which were (a)1 precedes 4 =12/24 (b) is the same as (a) since it is just in reverse. But I don't understand how to get the others. Thanks for any help.
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  2. #2
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    Quote Originally Posted by VGDude85 View Post
    Hey guys I need some help with this problem-
    What is the probability of these events when we randomly select a permutation of {1,2,3,4}?
    c)4 precedes 1 and 4 precedes 2
    d)4 precedes 1, 4 precedes 2, 4 precedes 3
    e)4 precedes 3 and 2 precedes 1

    I got (a) and (b) which were (a)1 precedes 4 =12/24 (b) is the same as (a) since it is just in reverse. But I don't understand how to get the others. Thanks for any help.
    c) The permutations that satisfy the given conditions are of the form:

    4 X X X
    3 4 X X

    How many of each form can you have ....?


    Apply similar logic to the remaining two questions.
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