To find the dimensions of the tray you need to work out the
angle through which the plate turns in one circuit and from that
the length of its circumference that comes into contact with the
edge of the tray as the plate rolls round.
You will need to use algebra to label the lengths of the side of
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.