### Why do this problem?

Provide training in conjecture, mathematical analysis and proof.
This difficult problem requires students to realise that it is
possible to use counting (a discrete process) to somehow categorise
different paths. This gives the power to make general
statements.

### Possible Approach?

First students need to calculate the end points of a few simple
roads. Although there are rational and irrational endpoints, group
discussion should lead to the conclusion that root 3 should be
involved in the irrational endpoints in some way.

### Key Questions?

If you have a valid road, how can its endpoint change with the
addition of a single tile? Two tiles?

Can you make any 'families' of roads which are similar, yet of
different lengths? Can you create expressions for the lengths of
these families of roads?