Back to Complex Numbers, Counting and Proof
Permutations: arrangements where order matters
Questions at easy, medium and hard levels. Pick a level and get a fresh set every time, with instant feedback.
Learn it The number of ways to arrange r things chosen from n, where order matters, is nPr = n!/(n − r)!. Arranging all n is n!. With repeated letters, divide by the factorial of each repeat.
Example: How many ways can 8 runners finish 1st, 2nd and 3rd?
- Order matters: 8P3 = 8 × 7 × 6.
- = 336.
Loading questions…