### Just Rolling Round

P is a point on the circumference of a circle radius r which rolls, without slipping, inside a circle of radius 2r. What is the locus of P?

### Coke Machine

The coke machine in college takes 50 pence pieces. It also takes a certain foreign coin of traditional design. Coins inserted into the machine slide down a chute into the machine and a drink is duly released. How many more revolutions does the foreign coin make over the 50 pence piece going down the chute? N.B. A 50 pence piece is a 7 sided polygon ABCDEFG with rounded edges, obtained by replacing AB with arc centred at E and radius EA; replacing BC with arc centred at F radius FB ...etc..

### Rotating Triangle

What happens to the perimeter of triangle ABC as the two smaller circles change size and roll around inside the bigger circle?

# Packing 3D Shapes

##### Stage: 4 Challenge Level:
Use your common sense and intuition as detailed calculations are exceedingly difficult and not really what the question is about.

Keep your eyes open for shapes in nature where 3D packing is exhibited

Once you are aware of 3D packing you will see that examples abound in nature. It is fascinating to ask: why does this packing of shapes occur?