Ten squares form regular rings either with adjacent or opposite
vertices touching. Calculate the inner and outer radii of the rings
that surround the squares.

If a is the radius of the axle, b the radius of each ball-bearing, and c the radius of the hub, why does the number of ball bearings n determine the ratio c/a? Find a formula for c/a in terms of n.

So Big

Age 16 to 18 Challenge Level:

What can you say about the tangents of the angles at the centre of
the circle?

Alternatively, can you see how you might calculate the area of
these 6 smaller triangles?