7 7 Scale Drawings Warm Up Problem of

7 -7 Scale Drawings Warm Up Problem of the Day Lesson Presentation Course 3

7 -7 Scale Drawings Learn to make comparisons between and find dimensions of scale drawings and actual objects. Course 3

7 -7 Scale Insert. Drawings Lesson Title Here Vocabulary scale drawing scale reduction enlargement Course 3

7 -7 Scale Insert Drawings Lesson Title Here Scale Interpretation 1: 20 1 unit on the drawing is 20 units. 1 cm: 1 m 1 cm on the drawing is 1 m. 1 4 in. = 1 ft 1 in. on the drawing is 1 ft. 4 Reading Math The scale a: b is read “a to b. ” For example, the scale 1 cm: 3 ft is read “one centimeter to three feet. ” Course 3

7 -7 Scale Drawings Additional Example 1 A: Using Proportions to Find Unknown Scales or Lengths A. The length of an object on a scale drawing is 2 cm, and its actual length is 8 m. The scale is 1 cm: __ m. What is the scale? 1 cm 2 cm scale length. = Set up proportion using xm 8 m actual length 1 8 = x 2 Find the cross products. 8 = 2 x 4=x Solve the proportion. The scale is 1 cm: 4 m. Course 3

7 -7 Scale Drawings Additional Example 1 B: Using Proportions to Find Unknown Scales or Lengths B. The length of an object on a scale drawing is 1. 5 inches. The scale is 1 in: 6 ft. What is the actual length of the object? 1 in. = 1. 5 in. Set up proportion using scale length. 6 ft x ft actual length 1 x = 6 1. 5 Find the cross products. x=9 Solve the proportion. The actual length is 9 ft. Course 3

7 -7 Scale Drawings Try This: Example 1 A A. The length of an object on a scale drawing is 4 cm, and its actual length is 12 m. The scale is 1 cm: __ m. What is the scale? 1 cm 4 cm scale length. = Set up proportion using xm 12 m actual length 1 12 = x 4 Find the cross products. 12 = 4 x 3=x Solve the proportion. The scale is 1 cm: 3 m. Course 3

7 -7 Scale Drawings Try This: Example 1 B B. The length of an object on a scale drawing is 2 inches. The scale is 1 in: 4 ft. What is the actual length of the object? 1 in. 2 in. = 4 ft x ft 1 x = 4 2 x=8 scale length. Set up proportion using actual length Find the cross products. Solve the proportion. The actual length is 8 ft. Course 3

7 -7 Scale Insert Drawings Lesson Title Here A scale drawing that is smaller than the actual object is called a reduction. A scale drawing can also be larger than the object. In this case, the drawing is referred to as an enlargement. Course 3

7 -7 Scale Drawings Additional Example 2: Life Sciences Application Under a 1000: 1 microscope view, an amoeba appears to have a length of 8 mm. What is its actual length? 1000 = 8 mm 1 x mm 1000 x=1 8 x = 0. 008 scale length actual length Find the cross products. Solve the proportion. The actual length of the amoeba is 0. 008 mm. Course 3

7 -7 Scale Drawings Try This: Example 2 Under a 10, 000: 1 microscope view, a fiber appears to have length of 1 mm. What is its actual length? 10, 000 = 1 mm 1 x mm 10, 000 x=1 1 x = 0. 0001 scale length actual length Find the cross products. Solve the proportion. The actual length of the fiber is 0. 0001 mm. Course 3

7 -7 Scale Insert Drawings Lesson Title Here 1 A drawing that uses the scale 4 in. = 1 ft 1 is said to be in in. scale. Similarly, a 4 drawing that uses the scale 1 in. = 1 ft is 2 in 1 in. scale. 2 Course 3

7 -7 Scale Drawings Additional Example 3 A: Using Scales and Scale Drawings to Find Heights A. If a wall in a 1 in. scale drawing is 4 in. tall, 4 how tall is the actual wall? 0. 25 in. = 4 in. 1 ft x ft. 0. 25 x=1 scale length actual length 4 x = 16 The wall is 16 ft tall. Course 3 Length ratios are equal. Find the cross products. Solve the proportion.

7 -7 Scale Drawings Additional Example 3 B: Using Scales and Scale Drawings to Find Heights B. How tall is the wall if a 1 in. scale is used? 2 0. 5 in. = 4 in. 1 ft x ft. 0. 5 x=1 scale length actual length 4 x=8 The wall is 8 ft tall. Course 3 Length ratios are equal. Find the cross products. Solve the proportion.

7 -7 Scale Drawings Try This: Example 3 A A. If a wall in a 1 in. scale drawing is 0. 5 in. 4 thick, how thick is the actual wall? 0. 25 in. = 0. 5 in. 1 ft x ft. 0. 25 x=1 scale length actual length 0. 5 x=2 The wall is 2 ft thick. Course 3 Length ratios are equal. Find the cross products. Solve the proportion.

7 -7 Scale Drawings Try This: Example 3 A Continued 1 B. How thick is the wall if a 2 in. scale is used? 0. 5 in. = 0. 5 in. 1 ft x ft. 0. 5 x=1 scale length actual length 0. 5 x=1 The wall is 1 ft thick. Course 3 Length ratios are equal. Find the cross products. Solve the proportion.

7 -7 Scale Insert. Drawings Lesson Title Here Lesson Quiz 1. What is the scale of a drawing in which a 9 ft wall is 6 cm long? 1 cm = 1. 5 ft 2. Using a 1 in. = 1 ft scale, how long would a 4 drawing of a 22 ft car be? 5. 5 in. 3. The height of a person on a scale drawing is 4. 5 in. The scale is 1: 16. What is the actual height of the person? 72 in. The scale of a map is 1 in. = 21 mi. Find each length on the map. 4. 147 mi 7 in. Course 3 5. 5. 25 mi 0. 25 in.