Permutations and combinations
From n distinct objects choose k without repetition.
Key knowledge
From n distinct objects choose k without repetition. Ordered selections number n!/(n−k)!; unordered selections number C(n,k)=n!/[k!(n−k)!]. The division by k! removes the orderings of each chosen subset.
Conditions and scope
- n,k are integers with 0≤k≤n and 0!=1.
- Repetition and indistinguishable objects require different counts.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Section 1.3 k-permutations, combination factorial formula and its double-counting derivation.
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Entry details
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- math-permutations-combinations
- Revision
- university-core.1
- Structured reference record
- University core expansion