Question 24
Colour the circles in the figure so that any two circles connected by a line segment have different colours. What is the least number of colours needed?
Interpretation: Only the marked circles are vertices; unmarked line crossings impose no extra colouring condition.
Answer format: enter a whole number without units. Leading zeros are optional.
Interpretation: Only the marked circles are vertices; unmarked line crossings impose no extra colouring condition.
Answer format: enter a whole number without units. Leading zeros are optional.