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Proportions and Scale Drawings Textbook Pages 417-422 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. • Scale 1 in : 8ft • If the scale model is 4 inches; What is the actual? • 32 feet • If the actual is size is 40 feet, what is the scale model? • 5 inches 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? • Covert both measurements to make the actual length and width. • 1cm 2cm 1cm 3cm 2m w 2m L Width is 4 m Length is 6 m Area is 4 x 6 = 24m squared Draw a diagram • Using the scale 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. Practice • Workbook Pages 107-108 1-12