A spherical balloon lies inside a wire frame. How much do you need
to deflate it to remove it from the frame if it remains a sphere?
Four Points on a Cube
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
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.