Use scales to find missing parts:

maps blueprints models

1. Use the similar parallelograms below.a) Find their scale factor.b) Find the ratio of their perimeters.

c) Find the ratio of their areas. 

2. Two similar figures have a perimeter of 4 m and 28 m.a) Find their scale factor.b) Find the ratio of their areas.

3. 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

Use the SCALE FACTOR !!!

Scale Factor is 2 : 3 Start your proportion with :

3

2

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. 2x = 80 x = 40

The actual distance is 40 miles.

miles

inches 16

miles 5

inches 2

x

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. 5x = 50 x = 10

The distance to Portland on the map is 10 inches.

miles 25

inches

miles 5

inches 2 x

A model car is made with a scale factor of 1 inch: 11 inchesThe actual car is 7 feet 4 inches long. How long is the model car?

Convert 7 feet 4 inches to inches to 7 ft 4 in = 7·12 + 4 match the scale factor: = 84 + 4 = 88 in

Write a proportion

Use cross products to solve. 11x = 88 x = 8

The model car is 8 inches long.

8811

1 x

A map has a scale of 2 inches : 5 miles.

Use the given distance on a map to find the actual distance.

1. 8 in

2. 1 ft 2 in

A model car has a scale of 1 : 24

3. If the model is 4 inches long, how long is the actual car in inches?

3. How long in feet?

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

Scale Drawings

Lesson 11