A friend asked me this question, and I am not sure I know how to answer it:(adsbygoogle = window.adsbygoogle || []).push({});

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I have 15 items, and I want to figure out how many unordered combinations of three there are. Any ideas?

a b c d e f g h i j k l m n o

Example:

abc bcd cde

abd bce cdf

abe bcf cde

abf bcg cdg

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The way Ithinkit can be done is using this formula:

[tex]

{n\choose k}={n!\over k!(n-k)!}

[/tex]

so you would have [tex]{15!\over 3!12!}[/tex] or455possible combinations.

But I am not really confident in this because I never studied this formula in a class - and I don't know if I am using it correctly.

Thanks!

-MIH

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# Figuring out # of possible combos of 3

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