Stage: 4 Challenge Level: 
An irregular tetrahedron has two opposite sides the same length ($a$ say) and the line joining their midpoints is perpendicular to these two edges and is of length $b$. What is the volume of the tetrahedron?
Visualising. Volume and capacity. Symmetry. Mathematical reasoning & proof. Pyramids. Working systematically. Real world. Graph sketching. Games. Tetrahedra.
Published October 2004.
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