Of unequal magnitudes the greater has to the same a greater ratio than the less has, and the same has to the less a greater ratio than it has to the greater.
Proof
Let a>b. Pick a multiplier n such that n(a−b)>c (the
Archimedean property of magnitudes, Definition V.4) and an m such
that mc falls between nb and na. Then na>mc but nb<mc;
by Definition V.7 this is precisely the assertion a:c>b:c.