¶The 21. Theoreme. The 23. Proposition. Numbers prime the one to the other: are ye least of any numbers, that haue one and the same proportion with them.
SVppose that A and B be numbers prime the one to the other. Then I say that A and B are the least of any numbers that haue one and the same proportion with them. For if A and B be not the least of any numbers that haue one and the same propor∣tion with them, then are there some numbers lesse then A and
B, being in the selfe same proportion that
A and
B are. Let the same be
C and D. Now forasmuch as the least numbers in any proportion measure any other numbers hauing the same pro∣portion equally, the greater the greater, and the lesse the lesse (by the
21. of the seuenth) that is, the antecedent the antece∣dent, and the consequent the consequent: therefore
C so many times measureth
A, as
D measureth
B. How many times
C measureth
A, so many vnities let there be in
E. Wherefore
D measureth
B by those vnities which are in
E. And forasmuch as
C measureth
A by those vnities which are in
E, therefore
E also measureth
A by those vnities which are in
C. And by the same reason
E measureth
B, by those vnities which are in
D. Wherefore
E measureth
A and
B being prime numbers the one to the other which (by the
13. definition of the seuenth) is impossible. Wherefore there are no other numbers lesse then
A and
B, which are in the selfe same proportion that
A and
B are. Wherefore
A and
B are the least numbers that haue one and the same proportion with them: which was required to be demonstrated.