Stage: 3 Challenge Level: 
A floor is covered by a tessellation of equilateral triangles, each having three equal arcs inside it. What proportion of the area of the tessellation is shaded?
Arcs, sectors and segments. Mathematical reasoning & proof. Angle properties of shapes. Pythagoras' theorem. Mixed triangles. Squares. smartphone. Visualising. Area. Circles.
Published April 1999.
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