Plant tree on tabular grid
Source: Vietnam Mathematical Olympiad 2016, Day 1, Problem 4
January 6, 2016
combinatorics proposedcombinatorics
Problem Statement
Let and be positive integers. A people planted two kind of different trees on a plot tabular grid size (each square plant one tree.) A plant called inpressive if two conditions following conditions are met simultaneously:
i) The number of trees in each of kind is equal;
ii) In each row the number of tree of each kind is diffrenent not less than a half of number of cells on that row and In each colum the number of tree of each kind is diffrenent not less than a half of number of cells on that colum.a) Find an inpressive plant when ;
b) Prove that if there at least a inpressive plant then and .