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Similarity Ratios and Proportions. Section 7.1. Ratio. Ways to write a ratio:. Be sure to SIMPLIFY!. Comparison of two quantities. Example. 4 to 18(12) = 4 to 216 = 1 to 54. 4:216 = 1:54. 4 = 1 216 54.
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SimilarityRatios and Proportions Section 7.1
Ratio Ways to write a ratio: Be sure to SIMPLIFY! Comparison of two quantities
Example 4 to 18(12) = 4 to 216 = 1 to 54 4:216 = 1:54 4 = 1 216 54 A scale model of a car is 4” long. The actual car is 18’ long. What is the ratio of the length of the model to the length of the car?
An Equation Proportion A statement that two ratios are equal Extended Proportion: When three or more ratios are equal
Cross-Product Property Means Extremes The product of the extremes is equal to the product of the means
Examples…solve the following proportions 1) 2 : 5 = n : 35 2) 3) 4) x + 1 : 3 = x : 2
Solving Proportions • Use the cross product property to solve for variables in a proportion
Solving an extended proportion • Choose two ratios to work with first in order to solve for a variable • Use substitution and then solve for the other variable using cross product
Properties of proportions: Cross Product Property Reciprocals Exchange the means Adding 1 to each side Given: The following is true: 1) 2) 3) 4)
Writing equivalent proportions • Given
Similarity Section 7.2
Similar • Two figures with the same shape that have: • Corresponding angles congruent • Corresponding sides proportional
Similarity Ratio = 2” 1 The ratio of the lengths of corresponding sides
To determine if two figures are similar Check that corresponding angles are congruent and all corresponding sides have an equal similarity ratio
Using Similar Figures Find the missing angles and side lengths given LMNP~QRST