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5.4: Scale Drawings

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Scale Factor The relationship between measurements on the drawings can be described by using a scale factor. When you make a drawing twice as wide and twice as tall, your scale drawing has a scale factor of 2:1. 1/2 inch on the original = 1 inch on the scale drawing.

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**measurement on model : measurement on actual or original**

Scale Factor So, the scale factor is always written as measurement on model : measurement on actual or original Or Original: Each square = ½ inch Drawing: Each square = 1 inch Scale Factor: 2:1 or 2/1

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**Simplifying the Scale Factor**

Original: Drawing: Each square= 1/2 inch Each square = 1/4 inch What is the scale factor on the smaller scale drawing of Calvin?

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**Scale Factor Scale factors are usually expressed using 1 unit.**

Real Eiffel Tower: 324 meters tall LEGO Eiffel Tower: meters tall. Instead of writing 1.08 : 324, we write 1 : 300 or 1/300

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Common Scale Factors House Plans/Floor Plans: ¼” scale, which means 1/4 inch stands for 1 foot: 1:48. N scale model trains: 1:148. Hot Wheels: 1:64 Radio-controlled car: 1:10 Traditional Dollhouses: 1:12, 1:18, or 1:24 Barbie Dollhouse: 1:6

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**Using scale factors: Practice**

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**Scale Models and Drawings are Proportional**

The reason a scale model or scale drawing looks similar to the actual or original thing is that all measurements on the model/drawing are proportional to measurements on the actual/original. This means that every part of the drawing is the same number of times bigger or smaller than the original or real thing. Stewie’s foot on the original drawing is ½ inch long. How long is Stewie’s foot on a 2:1 drawing? On a 0.5:1 drawing? If you made a 10:1 scale drawing of the original Stewie, how long would his foot be?

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Scale Another way to relate models to actual things is to use a scale, which includes units in different measurements.

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**Use a Proportion to Solve Scale Drawing/Model problems.**

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Practice

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Two figures are similar if… 1.) Their corresponding angles are congruent 2.) The corresponding sides are PROPORTIONAL!!! 5 in A B C D 4 in 10 in.

Two figures are similar if… 1.) Their corresponding angles are congruent 2.) The corresponding sides are PROPORTIONAL!!! 5 in A B C D 4 in 10 in.

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