Guichard-Combinatorics-Graph-Theory · Problem 2.2.10
Inclusion-Exclusion
Mathematics — Probability · derangements-coats-bags
Problem
On the way into a party everyone checks a coat and a bag at the door. On the way out, the attendant hands out coats and bags randomly. In how many ways can this be done if
((a)) No one gets either their own coat or their own bag?
((b)) One may get one's own coat, or bag, but not both.