Permutation

Permutation

• Nb of ways to order $N$ distinct objects $\to$ lists of ways $P(N)=N!$
• K-permutation “N pick K”: $P(N,K)=N\times (N-1)\times ...(N-K+1)=\frac{N!}{(N-K)!}$ ^165982
  • Only arrange K out of N distinct objects
• When objects are repeated: ${}_{a,b,c}{P}_N=\frac{n!}{a!b!c!}$