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# Starter - PowerPoint PPT Presentation

Starter. Scales!. Has anyone made a scale model before? What did you make? How would you explain what a scale model is?. Scale Models/Drawings. A scale model or a scale drawing is used to represent an object that is too large or too small to be drawn or built at actual size. Scal e.

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## PowerPoint Slideshow about 'Starter' - leonard-rowe

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Presentation Transcript
Scales!
• Has anyone made a scale model before?
• What did you make?
• How would you explain what a scale model is?
Scale Models/Drawings
• A scale model or a scale drawing is used to represent an object that is too large or too small to be drawn or built at actual size
Scale
• Definition: The scale gives the relationship between the measurements on the drawing or model and the measurements of the real object
• Ex: 1in = 3ft

1:24

Scale Factor
• The ratio of a length on a scale drawing to the corresponding length on the real object is called the scale factor
• If the scale is: 2in = 16 in
• Then the Scale factor is: 2/16 or 1/8
Scale Factor
• Another way to think about it is:
• What did you multiply the original amount by to get to the model size?
• Ex: Scale 2:6
• What did you multiply by?
• Scale factor is 3.
The relationship is proportional!
• Since the relationship of scales is proportional, we can use a proportion to determine missing values
• Ex: A set of landscape plans shows a flower bed that is 6.5 inches wide. The scale on the plans is 1 in = 4 feet. What is the width of the actual flower bed?
How to solve
• Use your scale factor as the first ratio
• Don’t forget to label!!!!
• Scale factor is 1 in/4 feet
• Make sure to line up the units correctly
• Actual measurement is 6.5 in/ x feet
Set up the proportion
• 1in/4ft = 6.5in/xft
• Cross multiply and solve!
• X = 26 ft
Determine the Scale

The inside of the Lincoln Memorial contains three chambers. The central chamber, which features a marble statue of Abraham Lincoln, has a height of 60ft. Suppose a scale model of the chamber has a height of 4 in. What is the scale?

How to solve
• Write the ratio of the height of the model to the height of the actual statue: 4in/60ft
• We want the scale in simplest form, so write your new ratio as 1/x
• Set up the proportion and solve

4in/60ft = 1in/x

4x = 60

x = 15 ft

Using scales
• Antonio is designing a room that is 20ft long and 12 ft wide. Find the lengths of the walls of the scale drawing of the room. Use the scale of 0.25in = 4ft
• Your second ratio is what you are trying to find. You will need write a ratio for each length
• Xin/20ft
• Win/12ft
Cont
• Scale.25in = x in

Actual 4ft 20ft

4x = (.25)20

4x = 5

X = 5/4 in or 1.25in

Scale.25in = w in

Actual 4ft 12ft

• 4w = (.25)12
• 4w = 3
• w = ¾ in or .75in