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In any proportion, the product of the means is equal to the product of the extremes.
The Youth's Assistant in Theoretic and Practical Arithmetic: Designed for ... - Page 73
by Zadock Thompson - 1832 - 168 pages

## The civil service arithmetic. [With] A key. [With] A key, Volume 1

Robert Johnston (F.R.G.S.) - 1879 - 318 pages
...proportion are called means (9 and 10); the first and fourth extremes (15 and 6). When four numbers form a proportion, the product of the means is equal to the product of the extremes. Thus, 6 : 3 : : 8 : 4 ; here, 6X4, the extremes, = 8X3, the means, = 24. form a proportion, the factors...

## Ray's New Higher Arithmetic: A Revised Edition of the Higher Arithmetic

Joseph Ray - Arithmetic - 1880 - 420 pages
...Simple when both ratios are simple ; Compound when one or both ratios are compound. PRINCIPLES. — 1. In every proportion the product of the means is equal to the product of Hie extremes. 2. The product of the extremes divided by either mean, iritt give the other mean. < 3....

## Ten years' Queen's scholarship questions, 1870-9, with answers to arithmetic ...

Education Ministry of - 1880 - 248 pages
...3'1416 its diameter. SECTION X. 1. Define ratio and proportion. Show that when four numbers are in proportion the product of the means is equal to the product of the extremes. 2. Explain, as to a class, the object and the process of reducing fractions to a common denominator....

## Geometry - Plane, Solid and Analytic Problem Solver

Research & Education Association Editors, Ernest Woodward - Mathematics - 2012 - 1080 pages
...congruent 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
...c are called 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...

## Merriam-Webster's Guide to Everyday Math: A Home and Business Reference

Brian Burrell - Mathematics - 1998 - 386 pages
...or as "/, = '//. The values b and c are referred to as the means; a and d are the extremes. In any proportion, the product of the means is equal to the product of the extremes. (This is also known as cross-multiplication.) THE RULE OF THREE "Do as you would be done by" is thought...