This is a standard treatment of the topic with two chapters
of extension material (not taught to my class this year) provided after the test.
(A minor update for September 2016)
2 HCF and LCM
3 Finding HCF and LCM of Pairs of Large Numbers
4 Factors and Multiples
7 Trapping The Primes (Extension Material)
8 'Not Prime' Proofs (Extension Matrerial)