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To express that the ratio of A to B is equal to the ratio of C to D, we write the quantities thus : A : B : : C : D; and read, A is to B as C to D.
Manual of Geometry and Conic Sections: With Applications to Trigonometry and ... - Page 70
by William Guy Peck - 1876 - 366 pages

## Plane and Solid Geometry

James Howard Gore - Geometry - 1898 - 232 pages
...AND PROPORTION. SIMILAR FIGURES. DEFINITIONS. 197. A Proportion is an equality of ratios. That is, if the ratio of a to b is equal to the ratio of c to d, they form a proportion, which may be written a:b — c:d, or - = -, or a:b::c:d, ba and is read a is...

## Transactions of the Cambridge Philosophical Society..

Cambridge Philosophical Society - Science - 1898 - 364 pages
...the measure of the ratio of A to B is the same as the measure of the ratio of C to D, and therefore the ratio of A to B is equal to the ratio of C to D. Hence any of the preceding propositions in which it has been proved that the scale of A, B is the same...

## Essentials of Geometry (plane).

Webster Wells - Geometry - 1898 - 250 pages
...POLYGONS. DEFINITIONS. 227. A Proportion is a statement that two ratios are equal. 228. The statement that the ratio of a to b is equal to the ratio of c to d, may be written in either of the forms a:b = c:d. or - = -- bd 229. The first and fourth terms of a...

## New School Algebra

George Albert Wentworth - Algebra - 1898 - 520 pages
...334. If the ratios a : b and с : d form a proportion, the proportion is written a : b = с : d (read the ratio of a to b is equal to the ratio of с to d), or a : b : : с : d (read a is to b in the same ratio as с is to d). The first and last...

## The Elements of Plane Geometry

Charles Austin Hobbs - Geometry, Plane - 1899 - 266 pages
...of equality between two ratios is called a proportion, and the four terms are called proportionals. If the ratio of a to b is equal to the ratio of c to d, the proportion may be expressed in either of the following forms : - = -, a:b = c:d, or a:b::c:d. bd They...

## Proceedings of the Edinburgh Mathematical Society

Edinburgh Mathematical Society - Electronic journals - 1899 - 342 pages
...A and B, the four magnitudes A, B, C, D are defined to be proportionals or to be in proportion when the ratio of A to B is equal to the ratio of C to D The proportion is often expressed by the notation A:B = C:D * or, in words, " A is to B as C is to D."...

## Plane Geometry

George Albert Wentworth - Geometry, Plane - 1899 - 272 pages
...: ij , jac a:o = c:d; a:b::c:d; T=3' oa This proportion is read, " a is to b as c is to d " ; or " the ratio of a to b is equal to the ratio of c to d." 324. The terms of a proportion are the four quantities compared ; the first and third terms are called...

## Plane and Solid Geometry

George Albert Wentworth - Geometry - 1899 - 500 pages
...ac a:o = c:a: a:o ::c:d; — = — • ba This proportion is read, " a is to b as c is to d " ; or " the ratio of a to b is equal to the ratio of c to d." 324. The terms of a proportion are the four quantities compared ; the first and third terms are called...