Stage: 5 Challenge Level: 
Take a cube of side length one unit. A vertex of the cube and the centres of the three faces not containing that vertex form the vertices of a tetrahedron. What is the surface area of this tetrahedron?
Tetrahedra. Long problems. Stage 5 - Reviewed 2012. Surface and surface area. Visualising. Games. Nets. Coordinates - 3D. Pythagoras' theorem. Cubes.
Published December 2000.
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