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Example 3-4b Objective Solve proportions

Example 3-4b Vocabulary Proportion When two ratios are equivalent

Example 3-4b Vocabulary Cross product The product of the numerator of one ratio and the denominator of the other ratio

Lesson 3 Contents Example 1Identify a Proportion Example 2Identify a Proportion Example 3Solve Proportions Example 4Solve Proportions

Example 3-1a Determine whether and form a proportion. Write a proportion. Find the cross products. Multiply. Answer: The ratios form a proportion 8(3) =? 12(2) 24 = 24 The cross products are equal 1/4 Check to see if equation is equal

Example 3-1b Determine whether and form a proportion. Answer: The ratios do not form a proportion 1/4

Example 3-2a Determine whether and form a proportion. Answer: The ratios do not form a proportion Find the cross products. 5(32) =? 8(18) Write a proportion Multiply. The cross products are not equal 2/4 Check to see if equation is equal

Example 3-2b Determine whether and form a proportion. Answer: The ratios form a proportion 2/4

Example 3-3a Solve Write the proportion. Find the cross products. Multiply. Ask “what is being done to the variable?” Do inverse on both sides The variable (n) is being multiplied by 3.5 3/4 Combine “like” terms 1  n 1  n = 24

Example 3-3a Solve Use the Identity Property to multiply 1  n 3/4 1  n = 24 n = 24 Answer:

Example 3-3b Answer: x = 25 Solve 3/4

Example 3-4a FLAGS According to specifications, the ratio of the length of the U.S. flag to its width must be 1.9 to 1. How long must a U.S. flag be if it is designed to have a width of 2.5 feet? length → width → Answer: L = 4.75 feet Write a proportion. length → width → Find the cross products. Multiply. 4/4 Add dimensional analysis

Example 3-4b SCHOOL The ratio of boys to girls at Blue Hills Middle School is 4 to 5. How many girls attend the school if there are 96 boys? Answer: x = 120 girls * 4/4

End of Lesson 3 Assignment Lesson 7:3 Algebra: Solving Proportions All