TOT 308 1991 Autumn A J5 coloured cells in 9x9 square
Source:
June 9, 2024
combinatoricsColoring
Problem Statement
A square is divided into unit cells. Some of the cells are coloured. The distance between the centres of any two coloured cells is more than .
(a) Give an example of colouring with coloured cells.
(b) Prove that the numbers of coloured cells cannot exceed .(S. Fomin, Leningrad)