JEE advanced - probability/combinatorics questions 

Questions 17 and 18 from the 2018 JEE Advanced Paper 1 cover probability and combinatorics. Q17 is about derangements, but I won't be using a formula for that; I'll just show you how to use systematic listing to find the answer. I'll also be covering what set intersection and union mean in the context of events in probability.
Past JEE advanced papers can be downloaded from jeeadv.ac.in/a...