Scale Drawings
Scale – The ratio that compares the
measurements of the real object and its
model. EX: 1 in = 6 ft
Scale factor – written as a ratio without
measurements and in simplest form
EX: the scale factor of 1 in = 6 ft is 1/72
Identify the scale factor.
Length (in.)
Actual
12
Model
2
Wing span (in.)
18
3
EX1)
model length
actual length
EX2)
=
2
12
Write a ratio using one of the
dimensions.
=
1
6
Simplify.
The scale is 1 inch = 3 feet. What is the scale factor?
1 inch = 1 inch
36 inches
3 feet
= 1
36
To eliminate units convert 3
feet to inches. Conversion
factor is 1 foot = 12 inches
EX3)
Find the Scale Factor from the following shape
small
large
Model
original
small
original
Model
large
3
3
12
12
Model
=
Original
3
Model
12
=
Original
1
Scale factor =
4
Scale factor =
12
3
4
1
EX4) A photograph was enlarged and made into a poster. The poster
is 20.5 inches by 36 inches.
The scale factor is 5 . Find the size of the photograph.
1. Draw a picture.
poster
20.5
photo
w
l
36
Think:
2. Write a proportion
to find the length l
and width w.
3. Solve the proportion.
poster = 5
= 36
l
photo
1
poster = 5 = 20.5
w
photo
1
36 X 1= 36
20.5 X 1= 20.5
36 ÷ 5 = 7.2
20.5 ÷ 5 = 4.1
Notes start here
assignment
Page 313
Problems 1-6
Date _______
Scaling Drawings
Scale – The ratio that compares the
_________________ of the _____ object
and its _______. EX: 1 in = 6 ft
Scale _______ – written as a ratio _______
measurements and in ________________
EX: the scale factor of 1 in = 6 ft is _______
Identify the scale factor.
EX1)
Actual
Model
Length (in.)
Wing span (in.)
model length
actual length
EX2)
=
Write a ratio using one of the
dimensions.
=
Simplify.
The scale is 1 inch = 3 feet. What is the scale factor?
1 inch =
3 feet
=
To eliminate units convert 3
feet to inches. Conversion
factor is __________________
EX3)
Find the Scale Factor from the following shape
small
large
Model
original
small
original
Model
large
3
3
12
12
Model
=
Original
Scale factor =
Model
=
Original
Scale factor =
EX4)
A photograph was enlarged and made into a poster. The poster
is 20.5 inches by 36 inches.
5
The scale factor is 1. Find the size of the photograph.
1.
2.
3.
Think:
poster
photo