Puzzles
Polygraph
Draw a regular polygon. Connect all its vertices to every other vertex. For example, if you picked a pentagon or a hexagon, the result would look as follows:
Colour the regions of your shape so that no two regions which share an edge are the same colour. (Regions which only meet at one point can be the same colour.)
What is the least number of colours which this can be done with?
Show answer & extension
Hide answer & extension
It can be done with two colours. Let's call these red and blue.
Draw the polygon and colour it red. As each line is added to is, swap the colours on one side of the line which leaving them the same on the other side. At the end of this process you will have any polygon coloured with two colours.
Extension
How many regions will the regular shape be split into by the lines?
![](javascript:showlimage("polygraph2.png"))
![](javascript:showlimage("polygraph1.png"))