Can I read 1987 IMO Problem 1: Fixed Points in Permutations on EtoBox?

1987 IMO Problem 1: Fixed Points in Permutations by Khant Si Thu is a document available to read on EtoBox.

What is 1987 IMO Problem 1: Fixed Points in Permutations about?

1) The sum counts the total number of fixed points in all n! permutations of numbers 1 to n. 2) Each number i from 1 to n has (n-1)! permutations where it is a fixed point. 3) Therefore, the total count of fixed points equals n(n-1)! = n!, proving the identity.

Author

Khant Si Thu

Language

EN