Many topological graphs have edges that cross. The aim is to re-draw the graph in such a way that none of the edges cross. The task informs students they are required to design a printed circuit board and since the wires are not insulated they must not cross.
Planarity: presentation - an introduction to the problem outlining the student task and putting the task into context.
Planarity: problem - a student version of the problem outlined in the introduction.
Planarity: solution - one possible suggested solution for the problem.
The OR Society have developed these problems for use in Decision mathematics lessons. The problems can be used as an introduction to a topic, part of the learning process or as a plenary exercise.