What happens to the perimeter of triangle ABC as the two smaller
circles change size and roll around inside the bigger circle?
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
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the
NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to
embed rich mathematical tasks into everyday classroom practice. More information on many of our other activities
can be found here.