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In any proportion, the product of the means is equal to the product of the extremes.
Elements of Plane and Solid Geometry - Page 202
by George Albert Wentworth - 1877 - 398 pages

## A Short History of Greek Mathematics

James Gow - Mathematics - 1884 - 350 pages
...would suffice for the discovery of many important rules, such for instance as that, in a proportion, the product of the means is equal to the product of the extremes. It is probable, therefore, that much of the Greek arithmetical knowledge dates from a time far anterior...

## Elements of Geometry and Trigonometry from the Works of A.M. Legendre ...

Charles Davies, Adrien Marie Legendre - Geometry - 1885 - 538 pages
...product is a fixed quantity, as xy = m. PROPOSITION I. THEOREM. If four quantities are in proportion, the product of the means is equal to the product of the extremes. Assume the proportion, BD A : B : : C : D ; whence A" = ~C- ' clearing of fractions, we have, BC =...

## School work, Volume 1

Frederick John Gladman - Classroom management - 1885 - 320 pages
...— the four numbers are in " proportion." 2 : 4 : : 3 : 6 (b) When four numbers are in proportion, the product of the means is equal to the product of the extremes. Define the terms "means" and "extremes," and illustrate the truth of the dictum by an example. In every...

## Principles of Arithmetic

Homersham Cox (the younger) - 1885 - 248 pages
...means. But whichever way it is written the theorem just proved can be stated thus— In any proportion the product of the means is equal to the product of the extremes. Since the product of 10 and 15 is equal to the product of 25 and 6 they both have the same ratio to...

## Geometry - Plane, Solid and Analytic Problem Solver

Research & Education Association Editors, Ernest Woodward - Mathematics - 2012 - 1080 pages
...angles. 10. AA = AA 11. Corresponding sides of similar triangles are in proportion. 12. In a proportion, the product of the means is equal to the product of the extremes. • PROBLEM 531 Using Ptolemy's Theorem show that if a anS b, with a ^ b, are chords of two arcs of...

## A Brief Course in Arithmetic

Ann Faber, Gale Edgerton, Paul Karanevich - Mathematics - 1985 - 254 pages
...proportion amounts to multiplying the "means" (inner numbers) and the "extremes" (outer numbers). If the product of the means is equal to the product of the extremes, the ratios are equal. 2X2 = 4 1:2 2:4 1 X4 = 4 4 = 4, so that 1 :2 = 2:4 is a proportion. I Example...

## Geometry I Essentials: Quick Access to the Important Facts and Concepts

Research and Education Association - Mathematics - 2015 - 112 pages
...the means of the proportion. The single term d is called the fourth proportional. In a proportion, the product of the means is equal to the product of the extremes. Theorem 2 A proportion may be written by inversion. (If alb = eld, then bla = die.) Theorem 3 •i...

## Basic Math Concepts: For Water and Wastewater Plant Operators

Joanne K. Price - Technology & Engineering - 1991 - 378 pages
...proportion. The inside terms (2nd and 3rd) are called the means of a proportion. For all proportions, the product of the means is equal to the product of the extremes. In other words, when the two inside terms are multiplied, the answer will be the same as when the two...