Or search by topic
The use of set terminology here should not hold anyone up as they can find the definition in the Thesaurus. This is an exercise in combinatorics and it also gives a method for solving the problem about the sequence of subsets.
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.
Explore some of the different types of network, and prove a result about network trees.
Label the joints and legs of these graph theory caterpillars so that the vertex sums are all equal.