1Define union and intersection, and give an example of each using two sets of your own.
2Why is n(A ∪ B) not simply n(A) + n(B)?
3Explain why A − B and B − A are usually different sets, with an example.
4What is the universal set, and why does a complement depend on it?
5In a class of 40, 25 study science, 18 study computing and 8 study both. Work out how many study only science, only computing, and neither.