Scale Drawing and Scale Models 7-5 Scale Drawing and Scale Models Course 3

Vocabulary Scale Drawing - a two-dimensional drawing that accurately represents an object. Scale - the ratio of the dimensions in the drawing to the dimensions of the actual object. Scale Model - a three-dimensional model that accurately represents a solid object.

1 unit on the drawing is 20 units. 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:4 m is read “one centimeter to four meters.” Reading Math

Using proportions to find actual lengths on a map: Video: https://www.bigideasmath.com/protected/content/dcs_cc2/tutorials/mp4/cc12/grade%207/chapter%205/section%204/ltut_7_05_04_1/ltut_7_05_04_1.html

We can use proportions to find unknown scale. For example: What is the scale of a drawing in which a 9 ft wall is 6 cm long? Set up a proportion and solve. Write the proportion as model to actual: 6cm/9ft = 1cm/xft The scale is 1 cm: 1.5 ft. (The model length is usually simplified to a measure of 1 to find the scale)

We can use proportions to find unknown 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. 1 cm x m 2 cm 8 m = Set up the proportion using model length . actual length Solve the proportion. (Multiply the cross product you know and divide by the third value. The scale is 1 cm:4 m.

Here is another example: 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. 1 cm x m 4 cm 12 m = Set up proportion using model length . actual length Solve the proportion. The scale is 1 cm:3 m.

Here is an example finding unknown length: Use 0.25 in = 1 ft scale, how long would a drawing of a 22 ft car be? Set up proportion using model length . actual length Solve the proportion. The scale drawing of the car would be 5.5 in long.

Your turn: Finding Unknown Dimensions Given Scale Factors A model of a 27 ft tall house was made using a scale of 2 in:3 ft. What is the height of the model? Set up a proportion and solve The height of the model is 18 in.

Let’s put an example in our notes

You Try: Example 3 A model of a 24 ft tall bridge was made using a scale of 4 in.:2 ft. What is the height of the model? Set up a proportion and solve. The height of the model is 48 in.

You Try: Example 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? Set up a proportion and solve. The height of the person is 72 in.