5.4: Scale Drawings
Scale Factor
• The relationship between
measurements on the
drawings can be described
by using a scale factor.
• When you make a drawing
twice as wide and twice as
tall, your scale drawing has
a scale factor of 2:1.
1/2 inch on the original =
1 inch on the scale drawing.
Scale Factor
• So, the scale factor is always written as
measurement on model : measurement on actual or original
Or
Original: Each square = ½ inch
Drawing: Each square = 1 inch
Scale Factor: 2:1 or 2/1
Simplifying the Scale Factor
Original:
Each square= 1/2 inch
Drawing:
Each square = 1/4 inch
What is the scale factor on the smaller scale
drawing of Calvin?
Scale Factor
Scale factors are usually expressed using 1 unit.
Real Eiffel Tower:
324 meters tall
•LEGO Eiffel Tower:
1.08 meters tall.
Instead of writing
1.08 : 324,
we write
1 : 300
or 1/300
Common Scale Factors
• House Plans/Floor Plans: ¼” scale, which
means 1/4 inch stands for 1 foot: 1:48.
• N scale model trains: 1:148.
• Hot Wheels: 1:64
• Radio-controlled car: 1:10
• Traditional Dollhouses: 1:12, 1:18, or 1:24
• Barbie Dollhouse: 1:6
Using scale factors: Practice
Scale Models and Drawings are Proportional
• The reason a scale model or scale drawing looks similar to the
actual or original thing is that all measurements on the
model/drawing are proportional to measurements on the
actual/original.
• This means that every part of the drawing is the same number
of times bigger or smaller than the original or real thing.
Stewie’s foot on the original drawing is ½ inch long.
• How long is Stewie’s foot on a 2:1 drawing?
• On a 0.5:1 drawing?
•
If you made a 10:1 scale drawing of the original
Stewie, how long would his foot be?
Scale
• Another way to relate models to actual things
is to use a scale, which includes units in
different measurements.
Use a Proportion to Solve Scale
Drawing/Model problems.
Practice