Combinatorics
\( nPr = \frac{n!}{(n-k)!} \quad nCr = \frac{n!}{k!(n-k)!} \)
Examples
- Poker (5 cards): \( \binom{52}{5} \)
- Seating (Line): \( n! \)
- Seating (Circle): \( (n-1)! \)
- Mississippi: \( \frac{11!}{4!4!2!1!} \)
Calculators & Helpers
\( nPr = \frac{n!}{(n-k)!} \quad nCr = \frac{n!}{k!(n-k)!} \)