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

************************************************

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

************************************************

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

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Figuring out # of possible combos of 3

**Physics Forums | Science Articles, Homework Help, Discussion**