Lesson 6-8: Cross Multiplication for Solving and Checking Proportions
In this lesson, we will learn how to use cross multiplication to solve proportions and check if two ratios form a proportion. Cross multiplication in a
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About Lesson 6-8: Cross Multiplication for Solving and Checking Proportions
PowerPoint presentation about 'Lesson 6-8: Cross Multiplication for Solving and Checking Proportions'. This presentation describes the topic on In this lesson, we will learn how to use cross multiplication to solve proportions and check if two ratios form a proportion. Cross multiplication in a. The key topics included in this slideshow are . Download this presentation absolutely free.
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Slide1+Lesson 6-8: Cross Multiplication Objective: We will learn to use cross multiplication to solve a proportion. We will use cross multiplication to check whether two ratios form a proportion.
Slide2+Cross multiplication, i n a proportion, is the product of one numerator and the other denominator. Property of Cross Products: If two ratios form a proportion, the cross products are equal. If 2 ratios have equal cross products, they form a proportion. Example 1: Decide whether each pair of ratios forms a proportion. You have to multiply the numerator with the denominator of the other fraction; and vice versa. 105 = =105 3×35 = 5 ×21 105 = 105 If the two products are equal, they form a proportion. When the cross products are not equal, the ratios do not form a proportion. v
Slide3+How to Solve a Proportion: For example : 4 = H Steps: 7 84 7×H = 4× 84 1. Write the cross products . 7H = 336 2. Multiply 7 H = 336 7 7 3. To find the value of the variable, undo the multiplication by dividing to both sides. H = 48 4. Divide (You have to think : The opposite of multiplication is division, so I have to divide the number that is with the variable and do the same for both sides of the problem. Then I cancel the opposites, and bring down what I have left. ) When solving a proportion you must cross multiply, then find the missing variable.
Slide4+Your Example : Solve the proportion. 2 = 3 4 N
Slide5+Homework: Textbook Pg. 311 #s 7-10 and 15-22. (Hint: In the first group answer yes or no, but you must show your work. In the second set of problems you must find the value of the variable by cross multiplying. )
