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Warm Up

Warm Up. The scale of a drawing is 4 in. = 12 ft. Find each actual measurement. 1. 6 in. 2. 2.5 in. The scale of a map is 1 in. = 3.5 mi. Find each length on the map. 3. 21 mi 4. 1.75 mi. 18 ft. 7.5 ft. 6 in. 0.5 in. Scale Models. 7.8. Pre-Algebra.

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Warm Up

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  1. Warm Up The scale of a drawing is 4 in. = 12 ft. Find each actual measurement. 1.6 in. 2. 2.5 in. The scale of a map is 1 in. = 3.5 mi. Find each length on the map. 3. 21 mi 4. 1.75 mi 18 ft 7.5 ft 6 in. 0.5 in.

  2. Scale Models 7.8 Pre-Algebra

  3. Learn to make comparisons between and find dimensions of scale models and actual objects.

  4. Vocabulary scale model

  5. Scale Model Very large and very small objects are often modeled. A scale model is a three-dimensional model that accurately represents a solid object. The scale model is mathematically similar to the solid object. A scale gives the ratio of the dimensions of the model to the actual dimensions.

  6. 1 in. 1 in. 1 1 1 yd 36 in. 36 36 The scale reduces the size of the actual object by a factor of . Example: Analyzing and Classifying Scale Factors Tell whether each scale reduces, enlarges, or preserves the size of the actual object. A. 1 in:1 yd = = Convert: 1 yd = 36 in. Simplify.

  7. 100 cm 1 m 10 cm 10 cm Example: Analyzing and Classifying Scale Factors Tell whether each scale reduces, enlarges, or preserves the size of the actual object. B. 1 m:10 cm Convert: 1 m = 100 cm. Simplify. = = 10 The scale enlarges the size of the actual object 10 times.

  8. 1 in. 1 in. 1 1 1 ft 12 in. 12 12 The scale reduces the size of the actual object by a factor of . Try This Tell whether each scale reduces, enlarges, or preserves the size of the actual object. A. 1 in:1 ft Convert: 1 ft = 12 in. Simplify. = =

  9. 12 in. 1 ft 1 ft 1 ft Try This Tell whether each scale reduces, enlarges, or preserves the size of the actual object. B. 12 in:1 ft = = 1 Convert: 12 in. = 1 ft. Simplify. The scale preserves the size of the actual object.

  10. 12 in 12 in. 6 ft 72 in. The scale factor is , or 1:6. 1 1 6 6 Example: Finding Scale Factors What scale factor relates a 12 in. scale model to a 6 ft. man? 12 in:6 ft State the scale. Write the scale factor as a ratio and simplify. = =

  11. 12 in 12 in. 4 ft 48 in. The scale factor is , or 1:4. 1 1 4 4 Try This What scale factor relates a 12 in. scale model to a 4 ft. tree? 12 in:4 ft State the scale. Write the scale factor as a ratio and simplify. = =

  12. = = 1 1 3 in. 1 in. 3 in. The scale factor for the model is . Now set up a proportion. 8 8 in. 24 in. 2 ft 8 h in. = 384 in. 1 8 Example: Finding Unknown Dimensions Given Scale Factors A model of 32 ft tall house was made using the scale 3 in:2 ft. What is the height of the model? = First find the scale factor. Convert: 32 ft = 384 in. 384 = 8h Cross multiply. 48 = h Solve for the height. The height of the model is 48 in.

  13. = = 1 1 4 in. 1 in. 4 in. The scale factor for the model is . Now set up a proportion. 6 6 in. 24 in. 2 ft 6 h in. = 288 in. 1 6 Try This A model of 24 ft tall bridge was made using the scale 4 in:2 ft. What is the height of the model? = First find the scale factor. Convert: 24 ft = 288 in. 288 = 6h Cross multiply. 48 = h Solve for the height. The height of the model is 48 in.

  14. = = 500,000,000 5 cm 50 mm 0.0000001 mm 0.0000001 mm Example: Life Science Application A DNA model was built using the scale 5 cm: 0.0000001 mm. If the model of the DNA chain is 20 cm long, what is the length of the actual chain? Find the scale factor. The scale factor for the model is 500,000,000. This means the model is 500 million times larger than the actual chain.

  15. 500,000,000 20 cm 1 x cm Example Continued = Set up a proportion. 500,000,000x = 1(20) Cross multiply. x = 0.00000004 Solve for the length. The length of the DNA chain is 4  10-8 cm.

  16. = = 2,000 2 cm 20 mm 0.01 mm 0.01 mm Try This A model was built using the scale 2 cm:0.01 mm. If the model is 30 cm long, what is the length of the actual object? Find the scale factor. The scale factor for the model is 2,000. This means the actual object is 2 thousand times larger than the model.

  17. 2,000 30 cm 1 x cm Try This Continued = Set up a proportion. 2,000x = 1(30) Cross multiply. Solve for the length. x = 0.015 The length of the actual object is 0.015 cm.

  18. Lesson Quiz: Part 1 Tell whether each scale reduces, enlarges, or preserves the size of the actual object. 1. 75 ft:40 in 2. 1 mi:1760 yd 3. 400 m:1 km 4. What scale factor was used to build a 5 in. model of a 60 ft statue? enlarges preserves reduces 1:144

  19. Lesson Quiz: Part 2 5. To create a model of the Eustachian tube of the human ear, an audiologist used the scale 1.5 cm = 0.6 mm. If the diameter of the Eustachian tube is 1.8 mm, what is the diameter of the model? 4.5 cm

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