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**

Dismiss Notice

Join Physics Forums Today!

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

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**