4. Permutations & Combinations

4.01 Introducing Factorials

4.02 A Password with 6 letters: How many arrangements?

4.03 Permutations and Combinations - what's the difference?

4.04a Permutations: Allowing Repetition

4.04b Permutations: Not allowing Repetition

4.05 Permutations: Introducing nPr

4.06 An Example of using nPr

4.07 A Password with 3 letters and 4 numbers: How many arrangements?

4.08 Introducing Combinations

4.09 Combinations: Introducing nCr

4.10 An Example of using nCr

4.11 A Second Example of using nCr

4.12 Permutations and Combinations: An Exam-Style Question