1. Scale Drawings & Scale Models
Created by:
Mrs. Dube

2. Vocabulary
Scale drawing – a proportional two-dimensional drawing of an object
Scale factor – the ratio used to enlarge or reduce similar figures
Scale model – a proportional three-dimensional model of an object
Scale – the ratio between two sets of objects

3. Finding a Scale Factor Create a ratio comparing the figures
Next, simplify the ratio
Ex. Use either lengths or heights to create the ratio to find the scale factor : 11/132 or 5.5/66
Simplify: ÷ by 11: 1/12 or 1/12
Race Car
Model
Length (in.)
132 11
Height (in.) 66
5.5

4. Using Scale Factor
Set up a proportion using the scale factor to find the unknown length
Cross multiply and then divide

5. Using Scale Factor
A photograph has dimensions 5.4 cm and 4 cm. The scale factor is 1/15. Find the size of the actual painting: photo/painting = 1/15
5.4/l = 1/ or 4/w= 1/15
l = 81 cm w = 60 cm
Dimensions of actual painting: 81cm x 60 cm

6. Measurement Application
Using scale factor to find distance
Set up proportion using scale factor and cross multiply and then divide to find missing distance

7. Scale Factor and Distance
The distance on a map between two cities is 10.5cm. The map scale is 3 cm = 128 km.
3/128 = 10.5/d
3d = Divide both sides by 3
d = 448 km