Stage: 4 Challenge Level: 
If you take the side length of the equilateral triangle as the unit for length, what would be the size of the hole ?
Alternatively, if the area of the yellow equilateral triangle is taken as the unit for area, what size is the hole then ?
Proof by contradiction. Tessellations. Continued fractions. Rational and irrational numbers. Stage 5 - Core Mapping. Mathematical reasoning & proof. Generalising. Equilateral triangles. Surds. Powers & roots.
Published February 2008.
Copyright © 2007. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project, which also includes the Plus and Motivate sites.
email: nrich@damtp.cam.ac.uk