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.
In how many distinct ways can six islands be joined by bridges so that each island can be reached from every other island...
The graph represents a salesman’s area of activity with the
shops that the salesman must visit each day. What route around the
shops has the minimum total distance?
Have a look at the nodes (the points where the lines meet).