1. How to write ratios and solve proportions. Chapter 7.1GeometryStandard/Goal: 1.3, 2.1, 4.1

2. 1. Check and discuss the assignment from yesterday. 2. Work and discuss warm up in small groups. 3. Read, write, and discuss how to write ratios and solve proportions. 4. Work on given assignment.

3. The photo of a building has the measurements given in the sketch below. The actual building is 26 ¼ ft wide. How tall is it? What is the height of the door in the actual building described in the drawing? Geometry

4. ratio is a comparison of two quantities. You can write the ratio of a to b or a : b as the quotient when

5. proportion is a statement that two ratios are equal. You can write a proportion in these forms:

6. Extended proportion when three or more ratios are equal. For example:

7. Cross-Product Property multiply both side of

8. 1. 2. 3. 4.

9. Scale Drawing A drawing in which all lengths are proportional to corresponding lengths. scale compares each length in the drawing to the actual length.

10. A scale model of a car is 4 in. long. The actual car is 15 ft long. What is the ratio of the length of the model to the length of the car? Write both measurements in the same units. 15 ft = 15 X 12 in. = 180 in. The ratio of the length of the scale model to the length of the car is 1 : 45. Lesson 7-1 4 in. 15 ft. ==== length of model length of car 4 in. 180 in. 4 180 1 45

11. ab = 48 Cross-Product Property Lesson 7-1 Complete: If =, then =. a4a4 12 b 12 ????  4b =4b =  4b4b Multiply each side by 4 b. a4a4 12 b = Divide each side by 12 a. 48 12 a ab 12 a = Simplify. 4a4a b 12

12. Solve each proportion. Cross-Product Property5 n = 2(35) Simplify.5 n = 70 Divide each side by 5. n = 14 Cross-Product Property3 x = 2( x + 1) Use the Distributive Property.3 x = 2 x + 2 Subtract 2 x from each side. x = 2 Lesson 7-1 = a. n 35 2525 b. = x2x2 x + 1 3

13. Two cities are 3 in. apart on a map with the scale 1 in. = 50 mi. Find the actual distance. 1212 d = 50 ( 3 ) 1212 Use the Cross-Product Property. d = 175Simplify. The cities are actually 175 mi. apart. Lesson 7-1 Let d represent the actual distance. = 1 in. 50 mi. Map distance (in.) actual distance (mi.) = 1 50 Substitute. 3d3d 1212 Additional Examples

14. Kennedy, D., Charles, R., Hall, B., Bass, L., Johnson, A. (2009) Geometry Prentice Hall Mathematics. Power Point made by: Robert Orloski Jerome High School.