Proportions and Scale Drawings
Textbook Pages 417-422
Objective
• I can solve scale drawing problems using
proportions.
Vocabulary
• Scale Drawing: is the same shape but not the
same size. A map is a scale drawing. The units
are very important.
• Scale: tells us how the drawings dimensions
and the actual dimensions are related. (Ratio)
• The standard way to write the scale is scale
model to actual object or scale:actual
Interpreting Scale Drawing
• 3 inches
• The scale is 1 in. : 5ft
• Find the actual length of
the canoe.
• 1in
3 in.
5ft
?ft
What did you do to 1 to
get to 3. Multiplied by 3.
So multiply 5 by 3 to get
15 ft.
• Scale 1 in : 8ft
• If the scale model is 4 inches; What is the
actual?
• 32 feet
• If the actual is size is 40 feet, what is the scale
model?
• 5 inches
Try some!
• The scale of a drawing 2 in.: 6m
• Length of the drawing = 8in.
• Length of object = __________
• Length of object = 36 m
• Length of drawing = __________
Word Problems
You are building a model boat with a scale of
1 in.:2ft.
The actual boat is 18 feet long.
How long should you make your model?
9 inches
Using it to find area and perimeter.
• A scale drawing of this classroom is 2cm by 3
cm. The scale is 1cm:2m. What is the area of
the classroom?
• Covert both measurements to make the actual
length and width.
• 1cm 2cm
1cm 3cm
2m w
2m
L
Width is 4 m
Length is 6 m
Area is 4 x 6 = 24m squared
Draw a diagram
• Using the scale 1in.:10ft, make a scale drawing
of a 30ft by 40 foot dance floor.
• You should have a 3in by 4 in drawing
• Use your drawing to find the actual distance
from opposite corners.
• If you measured on your scale drawing you
would find it to be 5 inches.
• Using the scale it would convert to 50 ft.
Practice
• Workbook Pages 107-108 1-12