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virtus

  • 2 years ago

Eight keys are placed on a key ring. How many different arrangements are possible if they are all different

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  1. IllasMcKay
    • 2 years ago
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    Pairs or ....

  2. virtus
    • 2 years ago
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    what do you mean?

  3. IllasMcKay
    • 2 years ago
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    just wait my Friend

  4. sauravshakya
    • 2 years ago
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    8 factorial

  5. IllasMcKay
    • 2 years ago
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    |dw:1342271877443:dw| then 8 factorial as @sauravshakya

  6. virtus
    • 2 years ago
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    my solution book says the answer is 7!/2

  7. virtus
    • 2 years ago
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    @myko where does the 2 come from?

  8. myko
    • 2 years ago
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    |dw:1342272266287:dw| |dw:1342272292346:dw| is the same in this case

  9. myko
    • 2 years ago
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    no, you right. The right answer is 7!/2

  10. virtus
    • 2 years ago
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    yes i thought so, because it is (n-1)!

  11. mukushla
    • 2 years ago
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    The total number of n objects, arranged in a circle which can be flipped over without making a new arrangement is: \[\frac{(n-1)!}{2}\]

  12. virtus
    • 2 years ago
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    thank you@mukushla

  13. myko
    • 2 years ago
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    it is (n-1)! and not n!, because there is no reference point. The reference point is the first key you put, so it's has to be rested from the total number of left posibilties. It is later devided by 2, becouse the ring can flip, so symetric permutations become the same

  14. virtus
    • 2 years ago
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    btw @myko does this rule apply to sitting in a circle arrangements

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