1. Use scales to find missing parts: maps blueprints models
Scale Drawings
Use scales to find missing parts:
maps
blueprints
models

2. Warm-Up Use the similar parallelograms below.
Find their scale factor.
Find the ratio of their perimeters.
Find the ratio of their areas. 
Two similar figures have a perimeter of 4 m and 28 m.
Find the ratio of their areas.
Two similar figures have a scale factor of 2 : 5.
If the larger figure has a perimeter of 40 ft,
what is the area of the smaller figure?
15 yd
24 yd

3. Use the SCALE FACTOR !!! Scale Factor is 2 : 3
Start your proportion with :

4. Example 1a Alan’s map has a scale of 2 inches : 5 miles.
The distance on the map from Mt. Hood Meadows to Alan’s
home is 16 inches. What is the actual distance?
Write a proportion.
Use cross products to solve x = 80
x = 40
The actual distance is 40 miles.

5. Example 1b Alan’s map has a scale of 2 inches : 5 miles.
The actual distance from Alan’s home to Portland is 25 miles.
Find the distance on the map.
Write a proportion.
Use cross products to solve x = 50
x = 10
The distance to Portland on the map is 10 inches.

6. Example 2 A model car is made with a scale factor of 1 inch: 11 inches
The actual car is 7 feet 4 inches long.
How long is the model car?
Convert 7 feet 4 inches to inches to ft 4 in = 7·12 + 4
match the scale factor: =
= 88 in
Write a proportion
Use cross products to solve x = 88
x = 8
The model car is 8 inches long.

7. 8 in 1 ft 2 in A map has a scale of 2 inches : 5 miles.
Use the given distance on a map to find the actual distance.
8 in
1 ft 2 in
A model car has a scale of 1 : 24
If the model is 4 inches long,
how long is the actual car in inches?
How long in feet?

8. Communication Prompt
When have you or a member of your family used a scale drawing? What information did it help you figure out?

9. Lesson 11
Proportionality
Scale Drawings