 | John Marsh (writing-master.) - Arithmetic - 1742 - 238 pages
...12, as 7 is to 28 ; or 3 is to 7, a» i2 is to 28. And when four Numbers.are thus Proportional, then the Product of the Means is equal to the Product of the Extreams. For 12x7=84 the Product of the Means. And 3x28=84 the Product of the Extreams. Wherefore... | |
 | Daniel Fenning - Algebra - 1802 - 274 pages
...in .if., either continued or interrupted (provided the interruption be between the 2d and 3d term), the product of the means is equal to the product of the extremes. EXAMPLE. Let the 4 numbers be 5, 15, 26, and 78 interrupted; then 5 x 78 = 15 x 26= 390. It will be... | |
 | Isaac Dalby - Mathematics - 1806 - 526 pages
...ac Or thus, since - z= -. • ba and f = > therefore 1=7. hdbh 68. If 4 quantities are proportional, the product of the means is equal to the product of the extremes. Thus suppose a : b : : c : d Then ad = he. For ? = ^ (s+)i and multiplying both fractions by W we have... | |
 | Charles Butler - Mathematics - 1814 - 528 pages
...given, — =6; if a, b, and c, are given, — =d; and be if d, b, and c, are given, then -r=a '• 60. If the product of two quantities be equal to the product of two others, then if the terms of one product be made the means, and the terms of the other product the extremes,... | |
 | James Wood - Algebra - 1815 - 338 pages
...three terms in a proportion being given, the fourth may be determined from the equation ad=bc. (175.) If the product of two quantities be equal to the product of two others, the four are proportionals, making the terms of one product the means, and the terms of the other, the... | |
 | Thomas Keith - Arithmetic - 1822 - 354 pages
...their numerators are equal, therefore AD=BC; A and D being the extremes, and B and c the means. 12. If the product of two quantities be equal to the product of two others, the four quantities may be turned into a proportion, by making the terms of one product the means, and... | |
 | George Lees - 1826 - 276 pages
...and, therefore, x = Vac. » 110. The converse of each of the preceding theorems is also true, that is, If the product of two quantities be equal to the product of two others, or if the product of two be equal to the square of one, then the FOUR, or the THREE quantities will... | |
 | Zadock Thompson - Arithmetic - 1828 - 238 pages
...price, and this must he ohvious from what was said in article 191. 195. Since, in every proportion, the product of the means is equal to the product of the extremes, one of these products may he taken for the other. Now if we divide the product of the means hy one... | |
 | Timothy Walker - Geometry - 1829 - 156 pages
...proportion. Thus 6 : 9 : : 10 : 15 : : 8 : 12 , is a continued proportion. 63. In every proportion, the product of the means is equal to the product of the extremes. For if two equal fractions be reduced to a common denominator, their numerators must be equal. Thus... | |
 | John Playfair - Geometry - 1829 - 210 pages
...greater than C, thenB is greater than D,if A=C,thenB=D,andif A be less than C, then B is less than D. 33. If the product of two quantities be equal to the product of two other quantities, these four quantities may be turned into a proportion by making the terms of one... | |
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In any proportion, the product of the means is equal to the product of the extremes. 
