1. Chapter 6 Lesson 3 Scale Drawings & Models pgs. 276-280
What you will learn:
Use scale drawings
Construct scale drawings

2. Vocabulary
Scale drawing/scale model (276): is used to represent an object that is too large or too small to be drawn or built at actual sizes
Scale (276): gives the relationship between the measurements on the drawing or model and the measurements of the real object
Scale factor (277): the ratio of a length on a scale drawing or model to the corresponding length on the real object

3. Scale Example: 1 inch = 3 feet
(One inch represents an actual distance of 3 feet)
1:24
(1 unit represents an actual distance of 24 units)

4. Scale Factor
Example: Suppose a scale model has a scale of 2 inches = 16 inches. The scale factor is 2 or 8
The lengths and widths of objects of a scale drawing or model are proportional to the lengths and widths of the actual object.

5. Example 1: Find Actual Measurements
A set of landscape plans shows a flower bed that is 6.5 inches wide. The scale on the plans is 1 inch = 4 feet.
What is the width of the actual flower bed?
Let x represent the actual width of the flower bed. Write and solve a proportion.
Plan width----> 1 inch = 6.5 inches<---plan width
Actual width--> 4 feet x feet <-----actual width
1x = 4 cross products
x= 26 The actual flower bed width is feet.

6. From the last example, what is the scale factor?
To find the scale factor, write the ratio of 1 inch to 4 feet in simplest form.
1inch = 1 inch Convert 4 feet
4 feet inches to inches
The scale factor is That is , each
measurement on the plan is 1 the actual measurement

7. Example 2: Determine the Scale
In a scale model of a roller coaster, the highest hill has a height of 6 inches. If the actual height of the hill is 210 feet, what is the scale of the model?
Model height---> 6 inches = 1 inch <--model height
Actual height--->210 feet x feet <--actual height
6x = 210
6x = x= 35
So, the scale is 1” =
35 feet

8. Example 3: Construct a Scale Drawing
A garden is 8 feet wide by 16 feet long. Make a scale drawing of the garden that has a scale of 1 in. = 2ft. 4
Step 1: Find the measure of the garden’s length on the drawing. Let x represent the length.
drawing length--> .25in = x in <--drawing length
actual length--> ft ft <---actual length
.2516 =2x
4 = 2x
2 = x
On the drawing, the length is 2 inches

9. drawing width--> .25 in = w inches <--drawing width
Step 2: Find the measure of the garden’s width on the drawing. Let w represent the width.
drawing width--> .25 in = w inches <--drawing width
actual width ---> 2 feet feet <---actual width
.258 = 2w
2 = 2w
1 = w
On the drawing the width is 1 inch.

10. 8 ft Step 3: Make the scale drawing.
Use 1/4” grid paper. Since 2” = 8 squares and 1 inch = 4 squares, draw a rectangle that is 8 squares by 4 squares.
< ft >
8 ft

11. Your Turn!
On a set of architectural drawings for an office building, the scale is 1/2” = 3 feet. Find the actual length of each room.
Lobby: 2 inches
Cafeteria: 8.25 inches
.5” = 2”
3ft x ft
.5x = The actual length
x = of the lobby is 12 ft
.5” = 8,25”
3ft x ft The actual length of the
.5x = cafeteria is 49.5 feet
x = 49.5

12. Your Turn, Again!
In an illustration of a honey bee, the length of the bee is 4.8 cm. The actual size of the honeybee is 1.2 cm. What is the scale of the drawing?
4.8 cm = 1cm
1.2 cm x cm
4.8x = 1.2
x = .25
The scale of the drawing is 1 cm = .25cm

13. Extra Practice sheets are by the door on your way out, be sure to grab one!
Quiz over 6-1 thru 6-3 Tomorrow!