— GEOMETOR • elements

G.169 part (measure) of a magnitude

A magnitude is a:term:**part** <part-aliquot> of a magnitude, the less of the greater, when it measures the greater.

G.170 multiple of a magnitude

The greater is a:term:**multiple** <multiple> of the less when it is:term:measured <part-aliquot> by the less.

If there be any number of magnitudes whatever which are, respectively, equimultiples of any magnitudes equal in multitude, then, whatever multiple one of the magnitudes is of one, that multiple also will all be of all.

G.172 magnitude multiple fifth

If a first magnitude be the same multiple of a second that a third is of a fourth, and a fifth also be the same multiple of the second that a sixth is of the fourth, the sum of the first and fifth is the same multiple of the second that the sum of the third and sixth is of the fourth.

G.173 ratio

A:term:**ratio** <ratio> is a sort of relation in respect of size between two magnitudes of the same kind.

G.174 ex aequali (equality of ratios)

A:term:ratio <G.173>ex aequali arises when, there being several magnitudes and another set equal to them in multitude which taken two and two are in the same proportion, as the first is to the last among the first magnitudes, so is the first to the last among the second magnitudes; Or, in other words, it means taking the extreme terms by virtue of the removal of the intermediate terms.

G.175 magnitude multiple equimultiples

If a first magnitude be the same multiple of a second that a third is of a fourth, and if equimultiples be taken of the first and third, then also :term:`ex aequali <G.174>` the magnitudes taken is equimultiples respectively, the one of the second and the other of the fourth.

G.176 magnitudes in the same ratio

Magnitudes are said to:term:**be in the same ratio** <in-the-same-ratio>, the first to the second and the third to the fourth, when, if any:term:equimultiples <multiple> whatever be taken of the first and third, and any equimultiples whatever of the second and fourth, the former equimultiples alike exceed, are alike equal to, or alike fall short of, the latter equimultiples respectively taken in corresponding order.

G.177 magnitude ratio equimultiples

If a first magnitude have to a second the same ratio as a third to a fourth, any equimultiples whatever of the first and third will also have the same ratio to any equimultiples whatever of the second and fourth respectively, taken in corresponding order.

G.178 magnitude multiple magnitude

If a magnitude be the same multiple of a magnitude that a part subtracted is of a part subtracted, the remainder is the same multiple of the remainder that the whole is of the whole.

G.179 magnitudes equimultiples magnitudes

If two magnitudes be equimultiples of two magnitudes, and any magnitudes subtracted from them be equimultiples of the same, the remainders also are either equal to the same or equimultiples of them.

G.180 proportional magnitudes

Let magnitudes which have the:term:same ratio <G.176> be called:term:**proportional** <proportional>.

G.181 corresponding magnitudes

The term:term:**corresponding magnitudes** <corresponding-magnitudes> is used of antecedents in relation to antecedents, and of consequents in relation to consequents.

G.182 invertendo (inverse ratio)

Inverse ratio means taking the:term:consequent <G.181> as antecedent in relation to the antecedent as consequent.

G.183 equal magnitudes ratio

Equal magnitudes have to the same the same ratio, as also has the same to equal magnitudes.

G.184 magnitudes having a ratio

Magnitudes are said to:term:**have a ratio** <have-a-ratio> to one another which are capable, when multiplied, of exceeding one another.

G.185 greater ratio

When, of the:term:equimultiples <multiple>, the multiple of the first magnitude exceeds the multiple of the second, but the multiple of the third does not exceed the multiple of the fourth, then the first is said to:term:**have a greater ratio** <greater-ratio> to the second than the third has to the fourth.

G.186 unequal magnitudes greater

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.

G.187 magnitudes ratio equal

Magnitudes which have the same ratio to the same are equal; and magnitudes to which the same has the same ratio are equal.

G.188 magnitudes ratio greater

Of magnitudes which have a ratio to the same, that which has a greater ratio is greater; and that to which the same has a greater ratio is less.

G.189 ratios ratio

Ratios which are the same with the same ratio are also the same with one another.

G.190 number magnitudes proportional

If any number of magnitudes be proportional, as one of the antecedents is to one of the consequents, so will all the antecedents be to all the consequents.

G.191 magnitude ratio greater

If a first magnitude have to a second the same ratio as a third to a fourth, and the third have to the fourth a greater ratio than a fifth has to a sixth, the first will also have to the second a greater ratio than the fifth to the sixth.

G.192 magnitude ratio greater

If a first magnitude have to a second the same ratio as a third has to a fourth, and the first be greater than the third, the second is greater than the fourth; if equal, equal; and if less, less.

G.193 parts ratio multiples

Parts have the same ratio as the same multiples of them taken in corresponding order.

G.194 alternando (alternate ratio)

Alternate ratio means taking the:term:antecedent <G.181> in relation to the antecedent and the consequent in relation to the consequent.

G.195 magnitudes proportional proportional

If four magnitudes be proportional, they is proportional alternately.

G.196 componendo (composition of ratio)

Composition of a ratio means taking the:term:antecedent <G.181> together with the consequent as one in relation to the consequent by itself.

G.197 separando (separation of ratio)

Separation of a ratio means taking the excess by which the:term:antecedent <G.181> exceeds the consequent in relation to the consequent by itself.

G.198 magnitudes proportional componendo

If magnitudes be proportional componendo, they is proportional separando.

G.199 magnitudes proportional separando

If magnitudes be proportional separando, they is proportional componendo.

G.200 convertendo (conversion of ratio)

Conversion of a ratio means taking the:term:antecedent <G.181> in relation to the excess by which the antecedent exceeds the consequent.

G.201 whole whole part

If, as a whole is to a whole, so is a part subtracted to a part subtracted, the remainder is to the remainder as whole to whole.

G.202 there magnitudes others

If there be three magnitudes, and others equal to them in multitude, which taken two and two are in the same ratio, and if :term:`ex aequali <G.174>` the first be greater than the third, the fourth is greater than the sixth; if equal, equal; and, if less, less.

G.203 perturbed proportion

A:term:**perturbed proportion** <perturbed-proportion> arises when, there being three magnitudes and another set equal to them in multitude, as:term:antecedent <G.181> is to consequent among the first magnitudes, so is antecedent to consequent among the second magnitudes, while, as the consequent is to a third among the first magnitudes, so is a third to the antecedent among the second magnitudes.

G.204 there magnitudes others

If there be three magnitudes, and others equal to them in multitude, which taken two and two together are in the same ratio, and the proportion of them be perturbed, then, if ex aequali the first magnitude is greater than the third, the fourth is greater than the sixth; if equal, equal; and if less, less.

G.205 there number magnitudes

If there be any number of magnitudes whatever, and others equal to them in multitude, which taken two and two together are in the same ratio, they is in the same ratio ex aequali.

G.206 there magnitudes others

If there be three magnitudes, and others equal to them in multitude, which taken two and two together are in the same ratio, and the proportion of them be perturbed, they is in the same ratio ex aequali.

G.207 magnitude ratio fifth

If a first magnitude have to a second the same ratio as a third has to a fourth, and also a fifth have to the second the same ratio as a sixth to the fourth, the first and fifth added together will have to the second the same ratio as the third and sixth have to the fourth.

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