Given the nets of 4 cubes with the faces coloured in 4 colours, build a tower so that on each vertical wall no colour is repeated, that is all 4 colours appear.
Label the joints and legs of these graph theory caterpillars so that the vertex sums are all equal.
Magic W
Age 14 to 16 Challenge Level
Even though this subject is accessible to school students, Magic
Graphs is currently an active research field (see Joseph Gallian's
website http://citeseer.ist.psu.edu/gallian00dynamic.html
which lists all the papers published on the subject).