Numbers were also the subject of Euclid Books VII to IX of Euclid’s Elements study properties of numbers. Divisors and multiples are part of a very old investigation that remains useful today. Your turn to investigate: Imagine two wheels marking steps: one from 4 to 4 and the other from 6 to 6. List the positive multiples. Where do brands meet for the first time? Discover the historical source on MacTutor, from the University of St Andrews.