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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

Manual of Algebra

William Guy Peck - Algebra - 1875 - 348 pages
...Definitions. 158. A proportion is an expression of equality between two ratios. A proportion may be written in two ways. Thus, if the ratio of a to b is equal to the ratio of c to d, we may indicate this equality by either of the following expressions: bd , - = - , or, a : b :: r,...

New Elementary Algebra: Containing the Rudiments of the Science for Schools ...

Horatio Nelson Robinson - Algebra - 1875 - 338 pages
...thus, a :,b : : c : d, which is read, a is to b, as c is to d ; or thus, a : b = c : d, which is read, the ratio of a to b is equal to the ratio of c to d. NOTE.— The second is the modern method, and more fitly expresses the nature of proportion. 253. A...

New University Algebra

Horatio Nelson Robinson - Algebra - 1875 - 430 pages
...of equality, : = : ; or a combination of points only, : : : : . Thus, .a : b = c : d, signifies that the ratio of a to b is equal to the ratio of c to d ; and the expression a : b : : c : d signifies the same, and may be read, a is to b as c is to d. 21....

New Elementary Algebra: Containing the Rudiments of the Science for Schools ...

Horatio Nelson Robinson - Algebra - 1879 - 332 pages
...thus, a : b : : c : d, which is read, a is to b, as c is to d ; or thus, a : b = c : d, which is read, the ratio of a to b is equal to the ratio of c to d. NOTE. — The second is the modern method, and more fitly expresses the nature of proportion. 24 •...

Algebra for Beginners: With Numerous Examples

Isaac Todhunter - Algebra - 1880 - 348 pages
...shortness we may say that the ratio of a to 6 is equal to т or is г . 349. Hence we may say that the ratio of a to b is equal to the ratio of с to d. when г = з • о а 350. ff the terms of a ratio be multiplied or divided by the same quantity...

University Algebra: Designed for the Use of Schools and Colleges

Webster Wells - Algebra - 1880 - 512 pages
...Thus, a : b, or - , indicates the ratio of a to b. o a : b = c : d, is a proportion. indicating that the ratio of a to b, is equal to the ratio of e to d, In a proportion the relation of the terms is such that the product of the first and fourth...

Elements of Algebra

George Albert Wentworth - Algebra - 1881 - 400 pages
...the ratios a : b and c : d form a proportion, the proportion is written , _ , a . o — c '. ct (read the ratio of a to b is equal to the ratio of c to d) or a : b : : c : d (read a is to b in the same ratio as c is to d). The first and last terms, a and...

Elements of Geometry, After Legendre, with a Selection of Geometrical ...

Charles Scott Venable - 1881 - 380 pages
...antecedent of the ratio, and for its denominator the consequent of the ratio. 3. Hence, we may say that the ratio of a to b is equal to the ratio of c to d. when - = - . bd 4. If the terms of a ratio be multiplied or divided by the same quantity, the ratio...