advertisement

Solving Proportions EXAMPLE 1 Solving Proportions Solve the proportion 4 = 12 20 . x METHOD - Use equivalent ratios. 4 4 = 12 12 5 20 x 5 12 X 5 = 60, so x = 60. ANSWER The solution is 60. GUIDED PRACTICE Solve the proportion using equivalent ratios. 1. n = 6 24 4 2. 25 = 10 5 k ANSWER ANSWER n 4 25 = 10 = 6 24 n = 1 k = 2 5 k GUIDED PRACTICE Solve the proportion using equivalent ratios. 3. 30 = 6 11 x 4. 10 = 4 s 12 ANSWER ANSWER 30 = 6 11 x 10 = 4 x = 55 s 12 s = 30 EXAMPLE 2 Solving Using a Verbal Model Boating: You are on a riverboat trip. You travel 5 miles in 3 hours. At that same rate, how long will it take you to travel 20 miles? SOLUTION Use a proportion. Let t represent the total time, in hours, of the 20 mile trip. Write a verbal model. Distance traveled Substitute values. Solve the proportion = Total distance Time traveled 20 mi 5 mi = th 3h 5 mi 3h = 20 mi 12 h Total time GUIDED PRACTICE for Example 2 5. What If? In Example 2, suppose you travel 4 miles in 2 hours. At that same rate, how long will it take you to travel 20 miles? ANSWER 4 mi = 20 mi th 2h 20 4 = t 2 t = 10h Proportions around us SCHOOL The ratio of boys to girls in history class is 4 to 5. How many girls are in the class if there are 12 boys in the class? Proportions at work • FACTORIES • A factory produces 6 motorcycles in 9 hours. • Write a proportion and solve it to find how many hours it takes to produce16 motorcycles. Proportions at home • COOKING • A recipe that will make 3 pies calls for 7 cups of flour. Write a proportion and solve it to find how many pies can be made with 28 cups of flour. Proportions in sports • BASKETBALL • The Lakewood Wildcats won 5 of their first 7 games this year. There are 28 games in the season. About how many games would you expect the Wildcats to win this season?