red squares in a 7x7 board
Source: 2022 May Olympiad L2 p1
September 4, 2022
Coloringcombinatorics
Problem Statement
In a board, some squares are painted red. Let be the number of rows that have an odd number of red squares and let be the number of columns that have an odd number of red squares. Find all possible values of . For each value found, give a example of how the board can be painted.