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SMO 2011 Junior Round 1 Question 7

SMO · SMO 2011 Junior Round 1

Question 7

The following annulus is cut into 14 regions. Each region is painted with one colour. What is the minimum number of colours needed to paint the annulus so that no two adjacent regions share the same colour?

Question illustration
  1. $3$
  2. $4$
  3. $5$
  4. $6$
  5. $7$