Question 69
We have five colours and a $99 \times 99$ grid. Some squares of the grid are coloured, each with one of the five colours, in such a way that
- Each colour appears the same number of times in the grid.
- No row and no column contains squares of different colours.
What is the largest possible number of squares that can be coloured following these rules?
- Each colour appears the same number of times in the grid.
- No row and no column contains squares of different colours.
What is the largest possible number of squares that can be coloured following these rules?