Standard formulas for permutations and combinations: ( {}^nP_r = \dfrac{n!}{(n-r)!} ), ( {}^nC_r = \dfrac{n!}{r!(n-r)!} ).
Accedmychevron_right11thchevron_rightmathchevron_rightPermutations And Combinationschevron_rightExercise 7.2
Standard formulas for permutations and combinations: ( {}^nP_r = \dfrac{n!}{(n-r)!} ), ( {}^nC_r = \dfrac{n!}{r!(n-r)!} ).