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Unformatted text preview: Pic tu re 1 Setting up cross-proportions (cross-multiplications) A cross-proportion is a mathematical expression of a problem that you are usually given in a form of a written text. For instance: If a dozen of donuts costs 4.95$, then how much does one donut cost? Let’s simplify: if 12 donuts cost 4.95 $ then 1 donut costs x Notice how “donut” lies underneath “donuts”. “Donuts” can be considered to be the “ units “ of the goods you are buying. Consequently, you can expect the “$” units to accompany the result for x. Let’s simplify the above even further, by losing the “if” and “then”, and replacing the “cost(s)” by a dash ( not a minus sign): 12 donuts- 4.95 $ 1 donut- x The above can be written into a four compartment box: 12 donuts 4.95 $ 1 donut x To solve for x, multiply the numbers in the two compartments that lie daigonally across from each other by each other, and divide the result by the number in the compartment that lies diagonally across from the one in which the x is located.from the one in which the x is located....
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This note was uploaded on 02/26/2009 for the course CHEM 1201 taught by Professor Cook during the Fall '08 term at LSU.
- Fall '08