Scale drawings and proportions

1. PROPORTIONS
AND SCALE
DRAWINGS
T E X T B O O K PA G E S 4 3 0 - 4 3 5

2. OBJECTIVE
• I can solve scale drawing problems
using proportions.

3. 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

4. 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.

5. 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 = __________

6. 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?

7. FINDING THE SCALE!
• A museum is creating a full sized T-Rex from a
model. The model is 40 inches in length. The
resulting dinosaur will be 40 feet tall in length.
What is the models scale?
• Write a ratio. Make sure both measures are in
inches. Then simplify.
• 40in = 40 in
40 ft 480 in
The model scale is 1:12