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Which triangles are similar?
8 20 12 4 10 8 Which triangles are similar? If they are in proportion they are similar.
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Ch. 4-3 Solving Proportions
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cross products two products found by multiplying the denominator of each ratio by the numerator of the other ratio 20 = 6 90 = 90 6 = 9
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proportion an equation stating that two ratios are equal – use cross products to determine if a proportion or not No, not a proportion 20 = 6 90 = 90 6 = 9 No, not a proportion Yes a proportion
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Example 1: Determine whether the following ratios form a proportion.
a.) b.) Yes, because cross products are equal 60 = 60 No, because cross products are not equal 10 = 8
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Example 2: Solve each proportion below by using the cross products.
a.) b.) c.) d.) Algebra Method: 2x = 90 Divide by 2 on both sides x = 45 Algebra Method: 12x = 84 Divide by 12 on both sides x = 7 Baby Math Method: (9*10)/2 Baby Math Method: (4*21)/12 Algebra Method: 15x = 180 Divide by 15 on both sides x = 12 Algebra Method: 8x = 72 Divide by 8 on both sides x = 9 Baby Math Method: (12*6)/8 Baby Math Method: (20*9)/15
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Example 3: Set up a proportion for each scenario below and solve by doing the cross products.
a.) Andy paid $1.29 for 3 pieces of candy. At that rate, what would 8 pieces of candy cost? b.) You are visiting friends in Estonia. Suppose the exchange rate is kroons = 1 dollar. How many Estonia kroons will you receive if you have $500? x = $3.44 Dollars Candy Kroons Dollar x = $6340
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#28 e.c. 4 pts. Show your steps for e.c.
Homework Pg. 177 #6-26 even (just answer) #28 e.c. 4 pts. Show your steps for e.c.
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