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This lesson focuses on solving proportions using cross products. Students will learn how to determine if a pair of ratios form a proportion and how to solve proportions by cross-multiplying and solving for the variable.
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Objective Students will solve proportions Chapter 8, lesson 2 (8-2).
Vocabulary: • Proportion • Cross products
Steps: • To determine whether each pair of ratios form a proportion you must do the following: * Cross multiply (N with D). * If products are =, they form a proportion. * Write final answer after showing all work.
Example: 2/13 , 4/26 (problem) 13 x 4 = 26 x 2 (cross X) 52 = 52 (look at answers) yes, it forms a proportion
Steps continued: • To solve each proportion, you must do the following: * Cross multiply (N with D) * Solve for the variable (letter) by dividing both sides by the # in front of the letter. * Write the final answer as Z = (letter = answer).
Example: 5/9 = w/54 (problem) 9 x W = 54 x 5 (cross M) 9W = 270 9w/9 = 270/9 (divide both sides by 9) W = 30 (answer)