Stage: 3 Challenge Level: 
An irregular tetrahedron is composed of four different triangles.
Can such a tetrahedron be constructed where the side lengths are 4, 5, 6, 7, 8 and 9 units of length?
How many different tetrahedra can be constructed?
Explain how you know you have found all the possible tetrahedra.
Games. Generalising. Mixed triangles. Working systematically. Visualising. Tetrahedra. Mathematical reasoning & proof. Interactivities. Cubes. Long problems.
Published June 2004.
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