Question 4
Nine circles are linked by crossing passages and coloured as follows (reading round the ring from the top left): purple, blue, yellow, green, red, purple, blue, green, red. Place the numbers 1 to 9 in the circles so that: (1) any set of three numbers that totals 15 (there are eight such sets) is on three different colours; (2) numbers of consecutive value are not directly linked by any passage.
