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Four quantities are proportional when the ratio of the first to the second is equal to the ratio of the third to the fourth.
Eaton's Elementary Algebra, Designed for the Use of High Schools and Academies - Page 87
by William Frothingham Bradbury - 1875

## Lessons in Geometry: For the Use of Beginners

George Anthony Hill - Geometry - 1888 - 202 pages
...77. I. Define a proportion. Four quantities are said to be proportional, or to form a proportion, if the ratio of the first to the second is equal to the ratio of the third to the fourth. For example: since ^ = f, the numbers 4, 10, 2, 5, are proportional. A h EF CDGH Again, the lines AB,...

## Lessons in Geometry: For the Use of Beginners

George Anthony Hill - Geometry - 1888 - 200 pages
...77. 1. Define a proportion. Four quantities are said to be proportional, or to form a proportion, if the ratio of the first to the second is equal to the ratio of the third to the fourth. For example: since T4T = ^, the numbers 4, 10, 2, 5, are proportional. ABEF CDGH Again, the lines AB,...

## Soule's Intermediate Philosophic Arithmetic, Embracing Oral and Written Problems

George Soulé - Arithmetic - 1888 - 568 pages
...and 8 are the consequents ; 3 and 8 are the extremes; and G and 4 are the means. 486. Three numbers .are proportional, when the ratio of the first to the second is equal to the ratio of the second to the third. Thus, 4, 8, and 16 are proportional, since 4 : 8 : : 8 : 16, each ratio be«g2....

## The Elements of Plane Geometry:pPart I(corresponding to Euclid Books I.-II ...

Association for the Improvement of Geometrical Teaching - Euclid's Elements - 1888 - 208 pages
...consequents, £, Q. DEF. 7. Three magnitudes (A, £, C) of the same kind are said to be proportionals, -when the ratio of the first to the second is equal to that of the second to the third ; that is, when A: B :: B : C. In this case C is said to be the third...

William Frothingham Bradbury, Grenville C. Emery - Algebra - 1889 - 428 pages
...A : Б and ?/? A : т В. 303. Proportion is an equality of ratios. Four numbers are in proportion when the ratio of the first to the second is equal...indicated by the sign of equality ( = ), or by four dots (: :). CL С Thus, a •: b = с : d, or a : b : : с : d, or - = - ; read, a to & bd equals с to...

William Frothingham Bradbury, Grenville C. Emery - Algebra - 1889 - 444 pages
...of A : Б and m A : т Б. 303. Proportion is an equality of ratios. Four numbers are in proportion when the ratio of the first to the second is equal...indicated by the sign of equality ( — ), or by four clots (: :). (1 С Thus, a : Ь = с : d, or a:b::c:d, or - = - ; read, a to о od equals с to d,...

## The Elements of Plane and Solid Geometry ...

Edward Albert Bowser - Geometry - 1890 - 414 pages
...EATIO AND PROPORTION. SIMILAE FIGURES. D'EFINITIOTSS. 277. Four quantities are said to be in proportion when the ratio of the first to the second is equal to the ratio of the third to the fourth. Thus, if £ = ° then, A, B, C, D are said to be in proportion. The proportion is written A : B = C...

## The Elements of Plane and Solid Geometry: With Numerous Exercises

Edward Albert Bowser - Geometry - 1891 - 424 pages
...KATIO AND PKOPOKTION. SIMILAR FIGUKES. DEFINITIONS. 277. Four quantities are said to be in proportion when the ratio of the first to the second is equal to the ratio oi the third to the fourth. Thus, if g = g, then, A, B, C, D are said to be in proportion. The proportion...