Then, since D is the same multiple of A that E is of B, while A is equal to B,
therefore D is equal to E.
But F is another, chance, magnitude.
If therefore D is in excess of F, E is also in excess of F, if equal to it, equal; and, if less, less.
And D, E are equimultiples of A, B, while F is another, chance, multiple of C;
therefore, as A is to C, so is B to C. [V. Def. 5]