Question 19
What is the largest number of cells that can be coloured on a $7 \times 7$ board in such a way that every $2 \times 2$ sub-board has at most $2$ coloured cells?
MathNet 2008-part-01 — 165 problems (EN–VI) Question 19
Math Olympiad Vault · MathNet 2008-part-01 — 165 problems (EN–VI)