Difference between revisions of "NCr"
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* [[nPr]] - the same concept but for number of [[permutations]] instead. | * [[nPr]] - the same concept but for number of [[permutations]] instead. | ||
* [[Pascal's triangle]] | * [[Pascal's triangle]] | ||
| + | ==Notes== | ||
| + | <references group="Note"/> | ||
| + | ==References== | ||
| + | <references/> | ||
| + | {{Definition|Combinatorics}} | ||
Latest revision as of 16:39, 14 April 2018
Stub grade: A
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I'd like this page to be better, "" for Combinations and what is noted there. Alec (talk) 16:38, 14 April 2018 (UTC)
Contents
[hide]Definition
n-choose-r is the number of ways to choose r items from n items, said differently it's the number of distinct combinations of length r we can make from n items.
- nCr(n,r):=n!r!(n−r)!
Notation
I write and prefer something like: nCr - but I've never gotten this to work well in LaTeX.
I've also seen (nr) used, but more compact (vertically) than this vector.
Properties
- nCr(n,r)=nCr(n,n−r)
See also
- nPr - the same concept but for number of permutations instead.
- Pascal's triangle
