7th Grade Math

Get ConnectED

Scale Drawings and Models

PART A B C

Multi-Part

Lesson 2

GLE 0706.2.3

Develop an understanding of

and apply proportionality.

SPI 0706.1.4 Use scales to

read maps. Also addresses

GLE 0706.1.4, GLE 0706.1.7,

SPI 0706.2.7.

284 Proportions and Similarity

Main Idea

Solve problems

involving scale

drawings.

Vocabulary

scale drawing

scale model

scale

scale factor

Scale Drawings

• Measure the length of each item
  basketball goal

basketball goal

bleacher bleacher

door door

in a room, such as a gymnasium.

• Record each length to the nearest
  _^1
  2
  foot.

1. Let 1 unit on the grid paper
   represent 2 feet. So, 4 units = 8 feet.
   Convert all your measurements
   to units.


2. On grid paper, make a drawing
   of your room like the one shown.

Scale drawings and scale models are used to represent objects that are

too large or too small to be drawn or built at actual size. The scale gives

the ratio that compares the measurements of the drawing or model to

the measurements of the real object. The measurements on a drawing

or model are proportional to the measurements on the actual object.

Use a Map Scale

MAPS What is the actual

distance between Hagerstown

97

595

270

MARYLAND

Annapolis

Hagerstown

1 cm = 24 miles

and Annapolis?

Step 1 Use a centimeter ruler

to find the map distance

between the two cities.

The map distance is

about 4 centimeters.

Step 2 Write and solve a proportion using the scale. Let d

represent the actual distance between the cities.

Scale Length

map

actual

__1 centimeter

24 miles

= __4 centimeters

d miles

map

actual

1 × d = 24 × 4 Cross products

d = 96 Simplify.

The distance between the cities is about 96 miles.

V

s

284_291_C05_L2_895130.indd 284 12/29/09 1:01 PM