The least numbers of those which have the same ratio with them measure those which have the same ratio the same number of times, the greater the greater and the less the less.
Proof
Given a:b=p:q with p, q least in their ratio, by VII.2
gcd(a,b)⋅p=a and gcd(a,b)⋅q=b, so p, q
each measure a, b the same number of times gcd(a,b).