Combinatorics · Colourings · Polyomino placements · Extremal count · Forcing argument
The cells of a \(4 \times 4\) table are to be coloured with several colours so that in every figure congruent to the one shown below, all four cells have different colours. The figure may be rotated or reflected, and placed anywhere inside the table.
What is the smallest number of colours for which such a colouring exists?
Sign in to check answers, open hints, read the full solution, and track your progress. Statements are always free.
Serbian Regional Competition (Okruzno takmicenje) 2021, high school grade I, category A, problem 4. Organized by the Mathematical Society of Serbia (DMS). Source