1. Math 009 Unit 5 Lesson 4

2. Obj: To determine whether a proportion is true A proportion is a statement of equality between two ratios or between two rates. 50 miles 25 miles 4 gallons 2 gallons = Notice that the units in the numerators of these rates are the same and the units in the denominators are the same. 3 1 6 2 =

3. Obj: To determine whether a proportion is true A proportion is true if the fractions are equal when written in simplest terms.  A proportion is true if the cross products are equal 2 8 3 12 = 3  8 = 24 2  12 = 24 The proportion is true. 4 8 5 9 = 5  8 = 40 4  9 = 36 The proportion is not true.

4. State whether the following are true proportions. 62 miles 33 miles 4 gallons 2 gallons 6 9 10 15 = = 4  33 = 132 62  2 = 124 The proportion is not true 10  9 = 90 6  15 = 90 The proportion is true

5. Obj: To solve a proportion Use the cross product rule to rewrite the equation Solve the new equation Check your answer Example: Solve n 25 12 60 = 60 n = 300 n 300  60 = n = 5

6. Obj: To solve a proportion Use the cross product rule to rewrite the equation Solve the new equation Check your answer Example: Solve 9 n 7 21 = 7n 189 = n 189  7 = n = 27

7. Obj: To solve a proportion Use the cross product rule to rewrite the equation Solve the new equation Check your answer Example: Solve n 14 5 9 = 9n 70 = n 70  9 = n = 7 7979

8. Obj: To solve a proportion Use the cross product rule to rewrite the equation Solve the new equation Check your answer Example: Solve 1.9 13 Round to the nearest 7 nhundredth = 1.9n 91 = n 91  1.9 = n  47.89

9. Obj: To solve application problems Three tablespoons of a liquid fertilizer are to be added to every 4 gallons of water. How many tablespoons of fertilizer are required for 10 gallons of water? 3 tablespoons n tablespoons 4 gallons 10 gallons = 4n 30 = n 30  4 = n = 7.5 Answer: 7.5 tablespoons should be added to 10 gallons

10. Obj: To solve application problems When engineers designed a new car, they first built a model of the car. The ratio of the size of a part on the model to the actual size of the part is 2:5. If a door is 1.3 feet long on the model, what is the length of the door on the car? 2 1.3 5 n = 2n 6.5 = n 6.5  2 = n = 3.25 Answer: The door on the real car will be 3.25 feet long Model 2 Real 5 =