### Nine Colours

Can you use small coloured cubes to make a 3 by 3 by 3 cube so that each face of the bigger cube contains one of each colour?

### The Spider and the Fly

A spider is sitting in the middle of one of the smallest walls in a room and a fly is resting beside the window. What is the shortest distance the spider would have to crawl to catch the fly?

### Hamiltonian Cube

Weekly Problem 36 - 2007
Find the length along the shortest path passing through certain points on the cube.

# The Perforated Cube

##### Age 14 to 16 Challenge Level:

This problem provides a rich context for visualisation and suggests many similar lines of enquiry.

For example :
• Can all letters of the alphabet be represented using only a 5 by 5 array of cubes ?

• Is it possible to create every combination of three letters in a 'perforated cube' ?

• What difference does the orientation of the letters make ?

• How many ways are there to orientate three non-symmetric letters such as F, J and P ?

• What difference will it make to use letters that have symmetry of some kind ?

For any chosen combination of letters and orientation, explore the variation possible in successful arrangements.
• Can every solution arrangement have either more cubes added or some removed, and still be a solution arrangement ?
• Is there a relationship between the maximum and minimum number of cubes for any solution ?
Exploring the perforated cube problem, and related questions, using clip-together plastic cubes will provide invaluable 'concrete' sensory experience for students as they stretch their powers of visualisation, express the problem, test their conjectures, or represent their solutions.

The information above is repeated on the Hint page which also contain this excellent video of one solution for E, S and H - video of an ESH solution