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# Combinations

A combination involves selecting elements from a set in a situation where order does not matter. For example, there are 3 ways to select 2 elements of the set $$\{ 1, 2, 3\}$$: $$\{1,2\}, \{1,3\}, \{2,3\}$$.

In general, to choose $$k$$ elements from a set with $$n$$ members, we use the binomial coefficient $${n \choose k} = \frac{n!}{k!(n-k)}!$$.

Note by Arron Kau
2 years, 5 months ago