MathDB

8

Part of 2005 Baltic Way

Problems(1)

25 x 25 grid of unit squares

Source: Baltic Way 2005/8

11/7/2005
Consider a 25×2525 \times 25 grid of unit squares. Draw with a red pen contours of squares of any size on the grid. What is the minimal number of squares we must draw in order to colour all the lines of the grid?
combinatorics proposedcombinatorics