Challenge Level

The solution is 18 square centimetres and everyone who submitted a response got it right. *Of special mention was the work of Sarah at Hethersett High School and Bryony with Sarah from Maidstone Girls' Grammar, all of whom had painstakingly set out their solutions complete with annotations and
diagrams.*

*Some people managed to spot that it there are multiple ways of drawing the shape; the point in the middle where the triangles 'kiss' can be moved left or right! Well done to those who realised that despite the variety of ways of drawing the shape, the area is always 18 cm ^{2}. Brilliant!*