Cross Products and Proportions

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Presentation transcript:

Cross Products and Proportions Proportion: two ratios that are equal. Cross Products: checks to see if ratio’s are proportional. Multiply opposite numerator and denominators together. If they equal , the ratio’s are proportional. Proportions Cross Product 3 2 3 2 = = 6 4 6 4 3 ∙ 4 = 6 ∙ 2 12 = 12

Are the following ratios Proportional? 5 1 8 10 = = 15 3 5 6 5 ∙ 3 = 15 ∙ 1 8 ∙ 6 = 5 ∙ 10 15 = 15 48 = 50 Yes No 6 9 6 4 = = 8 12 9 6 8 ∙ 9 = 6 ∙ 12 6 ∙ 6 = 9 ∙ 4 72 = 72 36 = 36 Yes Yes

Proportions with a variable To solve a proportion that contains a variable, you find the value that makes the equation true. Cross Product to solve 3 x 3 x = = 6 4 6 4 3 ∙ 4 = 6x 12 = 6x 12 ÷ 6 = 6x ÷ 6 2 = x

Solve each proportion 3 2 10 x = = x 6 12 6 3 ∙ 6 = 2x 10 ∙ 6 = 12x 18 = 2x 60 = 12x 18 ÷ 2 = 2x ÷ 2 60 ÷ 12 = 12x÷12 9 = x 5 = x