Ch 2 · Permutations and Combinations

5 concept points · 5 formulas · 4 exam-critical points.

📘 Core concepts

• 1Permutation: arrangement (order matters).
• 2Combination: selection (order does not matter).
• 3Factorial: n! = n(n−1)(n−2)...1; 0! = 1.
• 4Circular permutation of n distinct objects = (n−1)!
• 5Restrictions handled by treating grouped items as one unit or fixing positions.