Cum se calculează Combinations Permutations
Ce este Combinations Permutations?
Combinations count ways to choose items where order does not matter. Permutations count ways where order does matter. Both use factorials and appear in probability, statistics, and combinatorics.
Ghid pas cu pas
- 1Permutations (order matters): P(n,r) = n! / (n−r)!
- 2Combinations (order irrelevant): C(n,r) = n! / (r!(n−r)!)
- 3Rule of thumb: if you can swap two items and get a different result, use permutations
Exemple rezolvate
Intrare
Choose 3 from 10 (order matters)
Rezultat
720
P(10,3) = 10×9×8 = 720
Intrare
Choose 3 from 10 (order irrelevant)
Rezultat
120
C(10,3) = 720/6 = 120
Intrare
Lotto: 6 from 49
Rezultat
13,983,816
C(49,6)