1. = Divide each measure by the GCF, 3. drawing length actual length
Scale Drawings
LESSON 7-5
Additional Examples
The length of a drawing of a kitten is 3 cm. The actual length of the kitten is 27 cm. What is the scale of the drawing?
= Divide each measure by the GCF, 3.
3 cm
27 cm 1 9
drawing length
actual length
The scale is 1 cm to 9 cm, or 1 : 9.

2. Step 1 Write the scale as a ratio: . 1 inch 20 miles
Scale Drawings
LESSON 7-5
Additional Examples
Use a map scale of 1 in. : 20 mi to find the actual distance of 3.4 in.
Step 1 Write the scale as a ratio:
1 inch
20 miles
Step 2 Find the number of miles represented by 3.4 in.
Let y = the actual distance represented by 3.4 in.
map distances
actual distances =
1 in.
20 mi
3.4 in.
y mi
1y = 20 • 3.4 Write the cross products.
y = 68 Multiply.
The actual distance is 68 miles.

3. Write the scale as a ratio. model (cm) actual (m)
Scale Drawings
LESSON 7-5
Additional Examples
Suppose you are making a model of an 18-meter boat. Use a scale of 1 cm : 2.5 m to find the length of your model boat.
Write the scale as a ratio.
model (cm)
actual (m) 1
2.5
Use to represent the model length.
actual lengths 1
2.5 18 =
1 • 18 = 2.5 • Write the cross products.
18 = Multiply.
Divide each side by 2.5. 18
2.5 =
7.2 = Simplify.
The model will be 7.2 cm long.