Welcome to Math 6

Scale Factors

The Connector… A scale is the ratio between two sets of measurements.

A scale model is a proportional model of a three-dimensional object.

A scale drawing is a proportional drawing of an object.

OBJECTIVES:

Each student will:

1. Explain the meaning of the term scale factor.

2. Understand ratios and proportions in scale drawings and models.

3. Use ratios and proportions with scale.

Finding Scale Factor

How to identify scale factor.

Race Car

Model

Length (in.)

132 11

Height(in.)

66 5.5

EXAMPLE 1

How to identify scale factor.

Write a ratio using one of the dimensions. Then simplify the ratio.

To check your accuracy, write a ratio using another dimension and simplify. The ratio should be the same.

EXAMPLE 1

Guided Practice 1

What is the scale factor from triangle CAT to triangle DOG?

Use scale factor to find unknown lengths.

(When you know the scale factor and want to find the original or the scale model.)

EXAMPLE 2

Use scale factor to find unknown lengths.

Write a proportion using the scale factor and the known measurements.

EXAMPLE 2

Guided Practice 2

A scale model of the Empire State Building is 3.125 feet tall with a scale factor of 1/400. What is the height of the actual Empire State Building?

On a map, the distance between two cities is 10.5 cm. What is the actual distance between the cities if the map scale is 3 cm=80 mi?

EXAMPLE 3

Guided Practice 3The scale factor of a road map is 1cm = 30 mi. What is the actual distance between two cities if the distance on the map is 4.3cm?

Assignments

1. Scale Factor Worksheet

2. Scale Drawings and Models

PRACTICE

PRACTICE

PRACTICE

PRACTICE

Which of the MIDDLE circles looks bigger, the one on the left, or the one on the right?