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Math Help - Please help with word problem :)

  1. #1
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    Red face Please help with word problem :)

    So i have 6 different symbols! I need to make as many combinations of 4 of the 6 symbols as possible without using the same symbol more than once in a combination. How many possible combinations are there than meet that criteria and i would appreciate a formula if thats ok too. Thanks.
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  2. #2
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    6*5*4*3
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  3. #3
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    Is the * a multiplication sign?
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  4. #4
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    If it is a multiplication sign then that would mean 360 combinations of 4! But i cant have the same symbol used twice in a combination.
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  5. #5
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    Quote Originally Posted by GOST View Post
    If it is a multiplication sign then that would mean 360 combinations of 4! But i cant have the same symbol used twice in a combination.
    Is that an exclamation or 4 factorial?

    Yes, that is a multiplication symbol.

    Also, there are 6 choices the first time, 5 the next since we removed the item we already used, then 4 because 2 items are removed to avoid repetition, ....
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  6. #6
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    exclamation sorry. i havent used this forum before so im not used to the math lingo :/
    Yes yes, but for example lets say i have letters A B C D E F
    I want to make as many combinations of four as possible out of them;
    A B E D
    A B D F
    ..so on..
    but i cant have any repeat combinations and there cannot be any A A C E stuff going on either. No letter used twice.
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  7. #7
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    6 5 4 3
    _ _ _ _

    1st spot 6 choices, 2nd spot 5, 3rd 4, and 4th 3.

    6*5*4*3 = 360

    Didn't see you had the letters A-F.
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  8. #8
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    Thank you sooo much!!!
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  9. #9
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    I edited my original post.

    I didn't notice you had letters A-F.

    I thought you had A-D.
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  10. #10
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    Wow it just seems there are so many choices ya know! Thanks for your help btw, lol ive been annoying but im visual and the layout helped
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  11. #11
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    Just make spots for your choices when you do these problems.
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  12. #12
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    Will do thanks!!!
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  13. #13
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    Ok apperantly there is a missing piece to the puzzle. When trying to find all the possible combinations i came across multiple duplicates in combination. The spots are a great help yet they determine the total number of possible "orders" not combinations. For example when using the spots shown above i get this
    6 5 4 3
    _ _ _ _ This gives me 6 choices for spot 1 and 5 for spot 2 and so on so that the same letter isnt used over again in the sequence, BUT this is what happens:

    A B C D A C B D
    _ _ _ _ _ _ _ _ See. Although the sequence is different they are still the same combination :/ I need a way to determine only the possible combinations. Thank you.
    _ _ _ _
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  14. #14
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    nCr 6 choose 4

    \displaystyle \frac{n!}{r!(n-r)!}=\frac{6!}{4!(6-4)!}=\frac{6*5}{2!}=15
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