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Math Help - permutations

  1. #1
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    permutations

    1.a)Find the number of 4*4 patterns you can make using eight white,four grey,four blue tiles,

    my thinking \frac{16}{8!4!4!}=900,900

    b) How many different 10-digit telephone numbers contain four 2s three 3s and three 7s?

    c) A band has recorded five hit singles. In how many different orders could the band play three of these five songs at a concert?
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  2. #2
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    There is a problem with your first answer.
    Look at the graphs. They are all the same colorings.
    Do you see why?
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  3. #3
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by william View Post
    b) How many different 10-digit telephone numbers contain four 2s three 3s and three 7s?
    hint: find the number of ways to permute the 10 "objects" (the numbers here are the objects) and divide out the repeats (if you, for instance, switch one 2 with another, you get the same phone number, you must get rid of repeats so that you don't count the cases where you switch numbers with themselves).


    c) A band has recorded five hit singles. In how many different orders could the band play three of these five songs at a concert?
    hint: you have 5 choices for the first song, 4 for the second, and 3 for the third.
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