MathDB
Subtract from 720 You Must

Source: 2018 AIME II #11

March 23, 2018
AMCAIMEAIME II

Problem Statement

Find the number of permutations of 1,2,3,4,5,61,2,3,4,5,6 such that for each kk with 1≤k≤51\leq k\leq 5, at least one of the first kk terms of the permutation is greater than kk.
Back to ProblemsView on AoPS