Proportions and Scale Drawings Textbook Pages 430-435 Objective • I can solve scale drawing problems using proportions. Vocabulary • Scale Drawing: is the same shape but not the same size. A map is a scale drawing. The units are very important. • Scale: tells us how the drawings dimensions and the actual dimensions are related. (Ratio) • The standard way to write the scale is scale model to actual object or scale:actual Interpreting Scale Drawing • 3 inches • The scale is 1 in. : 5ft • Find the actual length of the canoe. • 1in 3 in. 5ft ?ft What did you do to 1 to get to 3. Multiplied by 3. So multiply 5 by 3 to get 15 ft. Try some! • The scale of a drawing 2 in.: 6m • Length of the drawing = 8in. • Length of object = __________ • Length of object = 36 m • Length of drawing = __________ Word Problems You are building a model boat with a scale of 1 in.:2ft. The actual boat is 18 feet long. How long should you make your model? 9 inches Using it to find area and perimeter. • A scale drawing of this classroom is 2cm by 3 cm. The scale is 1cm:2m. What is the area of the classroom? Draw a diagram • Using the scale model 1in.:10ft, make a scale drawing of a 30ft by 40 foot dance floor. • You should have a 3in by 4 in drawing • Use your drawing to find the actual distance from opposite corners. • If you measured on your scale drawing you would find it to be 5 inches. • Using the scale it would convert to 50 ft. Finding the scale! • A museum is creating a full sized T-Rex from a model. The model is 40 inches in length. The resulting dinosaur will be 40 feet tall in length. What is the models scale? • Write a ratio. Make sure both measures are in inches. Then simplify. • 40in = 40 in 40 ft 480 in The model scale is 1:12 Try some: • Find the model scale: • 5in 2ft 5/24 1ft 8yd 1/24 Practice • Workbook Pages 109-110 Even