Chapter 6 Lesson 3 Scale Drawings

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Chapter 6 Lesson 3Scale Drawings Modelspgs.
276-280

• What you will learn
• Use scale drawings
• Construct scale drawings

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Vocabulary

• Scale drawing/scale model (276) is used to
  represent an object that is too large or too
  small to be drawn or built at actual sizes
• Scale (276) gives the relationship between the
  measurements on the drawing or model and the
  measurements of the real object
• Scale factor (277) the ratio of a length on a
  scale drawing or model to the corresponding
  length on the real object

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Scale

• Example
• 1 inch 3 feet
• (One inch represents an actual distance of 3
  feet)
• 124
• (1 unit represents an actual distance of 24 units)

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Scale Factor

• Example Suppose a scale model has a scale of 2
  inches 16 inches. The scale factor is 2 or
  1
  16
• 8
• The lengths and widths of objects of a scale
  drawing or model are proportional to the lengths
  and widths of the actual object.

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Example 1 Find Actual Measurements

• A set of landscape plans shows a flower bed that
  is 6.5 inches wide. The scale on the plans is 1
  inch 4 feet.
• What is the width of the actual flower bed?
• Let x represent the actual width of the flower
  bed. Write and solve a proportion.
• Plan width----gt 1 inch 6.5 incheslt---plan width
• Actual width--gt 4 feet x feet lt-----actual
  width
• 1?x 4?6.5 cross products
• x 26 The actual flower bed width is
  26 feet.

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• From the last example, what is the scale factor?
• To find the scale factor, write the ratio of 1
  inch to 4 feet in simplest form.
• 1inch 1 inch Convert 4 feet
• 4 feet 48 inches to inches
• The scale factor is 1 . That is , each
  48
• measurement on the plan is 1 the actual
  measurement. 48

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Example 2 Determine the Scale

• In a scale model of a roller coaster, the highest
  hill has a height of 6 inches. If the actual
  height of the hill is 210 feet, what is the scale
  of the model?
• Model height---gt 6 inches 1 inch lt--model
  height
• Actual height---gt210 feet x feet lt--actual
  height
• 6?x 210
• 6x 210 x 35
• 6 6 So, the scale is 1
• 35 feet

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Example 3 Construct a Scale Drawing

• A garden is 8 feet wide by 16 feet long. Make a
  scale drawing of the garden that has a scale of 1
  in. 2ft.
• 4
• Step 1 Find the measure of the gardens length
  on the drawing. Let x represent the length.
• drawing length--gt .25in x in lt--drawing
  length
• actual length--gt 2 ft 16ft lt---actual
  length
• .25?16 2?x
• 4 2x
• 2 x
• On the drawing, the length is 2 inches

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• Step 2 Find the measure of the gardens width on
  the drawing. Let w represent the width.
• drawing width--gt .25 in w inches lt--drawing
  width
• actual width ---gt 2 feet 8 feet
  lt---actual width
• .25?8 2?w
• 2 2w
• 1 w
• On the drawing the width is 1 inch.

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• Step 3 Make the scale drawing.
• Use 1/4 grid paper. Since 2 8 squares and
  1 inch 4 squares, draw a rectangle that is 8
  squares by 4 squares.
• lt------------------------ 16
  ft---------------------gt
• 8 ft

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Your Turn!

• On a set of architectural drawings for an office
  building, the scale is 1/2 3 feet. Find the
  actual length of each room.
• Lobby 2 inches
• Cafeteria 8.25 inches

.5 2 3ft x ft .5x 6
The actual length x 12 of the
lobby is 12 ft
.5 8,25 3ft x ft The
actual length of the .5x 24.75
cafeteria is 49.5 feet x 49.5
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Your Turn, Again!

• In an illustration of a honey bee, the length of
  the bee is 4.8 cm. The actual size of the
  honeybee is 1.2 cm. What is the scale of the
  drawing?

4.8 cm 1cm 1.2 cm x cm 4.8x 1.2 x
.25 The scale of the drawing is 1 cm .25cm
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• Extra Practice sheets are by the door on your way
  out, be sure to grab one!
• Quiz over 6-1 thru 6-3 Tomorrow!