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

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

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

Course 3 7-7 Scale Drawings Additional Example 1A: 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 x m 2 cm 8 m Set up proportion using scale length . actual length = 1  8 = x  2 Find the cross products. 8 = 2x 4 = x Solve the proportion. The scale is 1 cm:4 m.

Course 3 7-7 Scale Drawings Additional Example 1B: 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. 6 ft 1.5 in. x ft Set up proportion using scale length . actual length = 1  x = 6  1.5 Find the cross products. x = 9 Solve the proportion. The actual length is 9 ft.

7-7 Scale Drawings Try This: Example 1A Course 3 7-7 Scale Drawings Try This: Example 1A 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 x m 4 cm 12 m Set up proportion using scale length . actual length = 1  12 = x  4 Find the cross products. 12 = 4x 3 = x Solve the proportion. The scale is 1 cm:3 m.

7-7 Scale Drawings Try This: Example 1B Course 3 7-7 Scale Drawings Try This: Example 1B 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. 4 ft 2 in. x ft Set up proportion using scale length . actual length = 1  x = 4  2 Find the cross products. x = 8 Solve the proportion. The actual length is 8 ft.

Insert Lesson Title Here Course 3 7-7 Scale Drawings Insert 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.

Additional Example 2: Life Sciences Application 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 1 = 8 mm x mm scale length actual length 1000  x = 1  8 Find the cross products. x = 0.008 Solve the proportion. The actual length of the amoeba is 0.008 mm.

7-7 Scale Drawings Try This: Example 2 Course 3 7-7 Scale Drawings Try This: Example 2 Under a 10,000:1 microscope view, a fiber appears to have length of 1mm. What is its actual length? 10,000 1 = 1 mm x mm scale length actual length 10,000  x = 1  1 Find the cross products. x = 0.0001 Solve the proportion. The actual length of the fiber is 0.0001 mm.

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

Additional Example 3A: Using Scales and Scale Drawings to Find Heights Course 3 7-7 Scale Drawings Additional Example 3A: Using Scales and Scale Drawings to Find Heights A. If a wall in a in. scale drawing is 4 in. tall, how tall is the actual wall? 1 4 0.25 in. 1 ft = 4 in. x ft. scale length actual length Length ratios are equal. Find the cross products. 0.25  x = 1  4 Solve the proportion. x = 16 The wall is 16 ft tall.

Additional Example 3B: Using Scales and Scale Drawings to Find Heights Course 3 7-7 Scale Drawings Additional Example 3B: Using Scales and Scale Drawings to Find Heights 1 2 B. How tall is the wall if a in. scale is used? 0.5 in. 1 ft = 4 in. x ft. scale length actual length Length ratios are equal. Find the cross products. 0.5  x = 1  4 Solve the proportion. x = 8 The wall is 8 ft tall.

7-7 Scale Drawings Try This: Example 3A Course 3 7-7 Scale Drawings Try This: Example 3A A. If a wall in a in. scale drawing is 0.5 in. thick, how thick is the actual wall? 1 4 0.25 in. 1 ft = 0.5 in. x ft. scale length actual length Length ratios are equal. Find the cross products. 0.25  x = 1  0.5 Solve the proportion. x = 2 The wall is 2 ft thick.

Try This: Example 3A Continued Course 3 7-7 Scale Drawings Try This: Example 3A Continued 1 2 B. How thick is the wall if a in. scale is used? 0.5 in. 1 ft = x ft. scale length actual length Length ratios are equal. Find the cross products. 0.5  x = 1  0.5 Solve the proportion. x = 1 The wall is 1 ft thick.

Insert Lesson Title Here Course 3 7-7 Scale Drawings Insert Lesson Title Here Lesson Quiz 1. What is the scale of a drawing in which a 9 ft wall is 6 cm long? 2. Using a in. = 1 ft scale, how long would a drawing of a 22 ft car be? 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? The scale of a map is 1 in. = 21 mi. Find each length on the map. 4. 147 mi 5. 5.25 mi 1 cm = 1.5 ft 1 4 5.5 in. 72 in. 7 in. 0.25 in.