Scale Drawings TeacherTwins©2014

Warm Up   X=2 X=30 X= 6 37.5 minutes

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A scale drawing is a proportional two-dimensional drawing of an object. When would you use a scale drawing?

The scale gives the relationship between the measurements on the drawing and the measurements of the real object. Examples: 1 inch = 3 feet 1 cm = 30 miles

You can also multiply 6.5 x 4 to get 26 ft. Example 1: A scale drawing of a garden has a flower bed that is 6.5 inches in length. The scale that was used for the drawing is 1 inch = 4 feet. What is the length of the actual flower bed? The flower bed is 6.5 inches on the drawing. The scale tells you that every inch on the drawing is equal to 4 feet in real life. Since every inch is 4ft in real life you can multiply 6 x 4 and get 24. The half inch is equal to 2 (half of 4 feet). Add the 2 to 24 and you get a length of 26 ft. You can also multiply 6.5 x 4 to get 26 ft.

What is the length of the actual flower bed? Example 1 continued: A scale drawing of a garden has a flower bed that is 6.5 inches in length. The scale that was used for the drawing is 1 inch = 4 feet. What is the length of the actual flower bed?     We are going to write a proportion using the scale of the drawing. The actual length of the flower garden is 26 ft.

s Example 1B: A scale drawing of a garden uses a scale that is 1 inch = 4 feet. If the garden is 12 feet in length how long will it be on the scale drawing? The garden is 12 feet in length. Twelve divided by 4 gives you the length on the drawing which is 3 inches. For every 4 feet in real life you have one inch on the scale drawing. You can also think of it this way: 12 feet can be divided into 3 groups of 4 feet. 4 ft. 4ft. 4ft. 1 in 1 in 1 in 12 feet 3 inches

The length of the flower garden on the drawing is 3 in. Example 1B continued: A scale drawing of a garden uses a scale that is 1 inch = 4 feet. If the garden is 12 feet in length how long will it be on the scale drawing? We are going to write a proportion using the scale of the drawing.   1 in x inches = 4 feet 12 feet The length of the flower garden on the drawing is 3 in.

Example 2: Finding Scales Find the scale used on a scale drawing of a bedroom if the actual length is 13 meters and the length on the scale drawing is 2.5 centimeters. We will find what 1 cm is equal to in the drawing, so we put a 1 to represent the drawing. To find the scale, look at the measurement of the scale drawing and the actual object and put them in your proportion.       The scale used for the drawing is 1 cm = 5 m.

Practice      

Practice 3). What is the scale on a map, if the distance in real life is 50 miles and the distance on the map is 2.5 inches? 4). Marci has a scale drawing of her new bedroom. On the drawing the length of the bedroom is 2 cm. In real life her bedroom is going to be 7 meters in length. What is the scale of the drawing?    

Closure Give an example of when you would use scale drawings or scales in real life.