Combinatorics · Grid domination · Counting bounds · Extremal constructions · Perfect coverings
Problem 2, 2024
Borut drew the table of size \(2 \times 7\) shown in the picture. He now wants to colour some of its cells so that every cell he leaves uncoloured shares a side with at least one coloured cell. What is the smallest number of cells he has to colour?
- A \(3\)
- B \(4\)
- C \(5\)
- D \(6\)
- E \(7\)
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Slovenian High School Mathematics Competition for Vega Awards (MaSSA), drzavno (national) round 2024, 1. letnik, category A, problem A2. Organized by DMFA Slovenije (Society of Mathematicians, Physicists and Astronomers of Slovenia). Source