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If the product of two quantities is equal to the product of two other quantities, two of them may be made the extremes, and the other two the means of a proportion.
New Elementary Algebra Embracing the First Principles of the Science - Page 266
by Charles Davies - 1891 - 294 pages

## An Introduction to Algebra: Being the First Part of a Course of Mathematics ...

Jeremiah Day - Algebra - 1814 - 304 pages
...=-jtyeducing the fractions, ad=bc. Thus 12: 8:: IS: 10, therefore 12x10=8x15. 375. On the other hand, if the product of two quantities is equal to the product of two others, the four quantities will form a proportion, when they are so arranged, that those .on one side...

## An Introduction to Algebra: Being the First Part of a Course of Mathematics ...

Jeremiah Day - Algebra - 1827 - 352 pages
...is, in both cases the same. And if no : b'. '.x : yy then a : b'.'.x : ny. 375. On the other hand, if the product of two quantities is equal to the product of two others, the four quantities will form a proportion, when they are so arranged, that those on one side...

## Elements of Algebra

Algebra - 1838 - 372 pages
...B, C, and D, are so related to each other that AxD=B*C, i „ , , BD we shall also have ~T=~r' A. O and hence, A : B : : C : D; that is, if the product...extremes, and the other two the means of a proportion. 180. If we have three proportional quantities A : B : : B : C, 1 ^ C wehave _=_; hence, &=AC; that...

## Elements of Algebra

Bourdon (M., Louis Pierre Marie) - Algebra - 1839 - 368 pages
...product of the two means. 179. If four quantities, A, B, C, and D, are so related to each other that we shall also have — =— , AC/ and hence, A : B...product of two quantities is equal to the product of two otter quantities, two of them may be made the extremes, and the other two the means of a proportion....

## First Lessons in Algebra: Embracing the Elements of the Science

Charles Davies - Algebra - 1839 - 264 pages
...B, C, D, are so related to each other that AxD=BxC, ,....., BD we shall also have — =— ; A. Lx and hence, A : B~: : C : D. That is : If the product of two quantities is equal to tJte product of two other quantities, two of them may be made the extremes, and the other two the means...

## First Lessons in Algebra: Embracing the Elements of the Science

Charles Davies - Algebra - 1840 - 264 pages
...quantities, A, B, C, D, are so related to each other that ta.ll.!! BD we shall also have — =— ; AO and hence, A : B : : C : D. That is : If the product of two quantities is equal to the product of two otlier quantities, two of them may be made the extremes, and the other two the means of a proportion....

## First Lessons in Algebra: Embracing the Elements of the Science

Charles Davies - Algebra - 1841 - 264 pages
...D, are so related to each other that AxD=BxC, . . . . , BD we shall also have — =— ; -j' I ' ' and hence, A : B : : C : D. That is : If the product...extremes, and the other two the means of a proportion. ThuB, if we have 2x8=4x4, we also have 2 : 4 : : 4 : 8. 156. If we have three proportional quantities...

## Elements of Algebra

Charles Davies - Algebra - 1842 - 368 pages
...quantities, A, B, C, and D, are so related to each other that we shall also have — =— ., jfi O and hence, A : B : : C : D; that is, if the product...extremes, and the other two the means of a proportion. we have -=^; , BC hence, B 2 =AC; that is, the square of the middle term is equal to the product of...