### Far Horizon

An observer is on top of a lighthouse. How far from the foot of the lighthouse is the horizon that the observer can see?

### More or Less?

Are these estimates of physical quantities accurate?

### Investigating the Dilution Series

Which dilutions can you make using only 10ml pipettes?

# Efficient Packing

##### Stage: 4 Challenge Level:

How efficiently can you pack disks of the same size with no overlap? Imagine attempting to cover a 1m square with 10cm diameter disks with no overlap. What percentage of the area of the square can you actually cover using this obvious packing for disks?

How much more efficiently would you be able to pack 1cm diameter disks into the 1m square? Could you make an estimate for the efficiency of packing disks of diameter 1mm?

• As a harder extension, make an estimate of the number of 1cm diameter balls that would be able to fit into a 1m cubed box.

#### Notes and background

Whilst it might seem relatively simple, the problem of 'shape packing' is often very difficult mathematically to solve with certainty for many shapes. Intuitive visualisation often works just as well as a strict mathematical analysis, and often is the only sensible possibility with packing together complicated shapes.

You might like to consider situations in which efficient shape packing is relevant in the physical world.