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Unformatted text preview: Â§ 7.6 Proportions and Problem Solving with Rational Equations MartinGay, Beginning Algebra, 5ed 2 Ratios and Rates Ratio is the quotient of two numbers or two quantities. The units associated with the ratio are important. The units should match. If the units do not match, it is called a rate , rather than a ratio. The ratio of the numbers a and b can also be written as a : b , or . b a MartinGay, Beginning Algebra, 5ed 3 Proportion is two ratios (or rates) that are equal to each other. d c b a = We can rewrite the proportion by multiplying by the LCD, bd. This simplifies the proportion to ad = bc. This is commonly referred to as the cross product . Proportions MartinGay, Beginning Algebra, 5ed 4 Solve the proportion for x . 3 5 2 1 = + + x x ( 29 ( 29 2 5 1 3 + = + x x 10 5 3 3 + = + x x 7 2 = x 2 7 = x Solving Proportions Continued. Example: MartinGay, Beginning Algebra, 5ed 5 3 5 2 3 2 5 = true Substitute the value for x into the original equation, to check the solution. So the solution is 2 7 = x 7 2 7 1 5 3 2 2 + = + Solving Proportions Example continued: MartinGay, Beginning Algebra, 5ed 6 If a 170pound person weighs approximately 65 pounds on Mars, how much does a 9000pound satellite weigh? Mars on satellite pound x Mars on person pound 65 Earth on satellite pound 9000 Earth on person pound 170 = 000 , 585 65 9000 170 = â‹… = x pounds 3441 170 / 585000 â‰ˆ = x Solving Proportions Example: MartinGay, Beginning Algebra, 5ed 7 Given the following prices charged for various sizes of picante sauce, find the best buy....
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 Spring '09
 prescott
 Algebra, Equations, Ratios, Ratio

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