1. 7-7 Scale Drawings Warm Up Problem of the Day Lesson Presentation
Course 3
Warm Up
Problem of the Day
Lesson Presentation

2. Course 3
7-7
Scale Drawings
Learn to make comparisons between and find dimensions of scale drawings and actual objects.

3. Insert Lesson Title Here
Course 3
7-7
Scale Drawings
Insert Lesson Title Here
Vocabulary
scale drawing
scale
reduction
enlargement

4. Insert Lesson Title Here Scale Interpretation
Course 3
7-7
Scale Drawings
Insert Lesson Title Here
Scale
Interpretation
1:20
1 unit on the drawing is 20 units.
1 cm: 1 m
1 cm on the drawing is 1 m.
in. = 1 ft
in. on the drawing is 1 ft.
1 4
1 4
The scale a:b is read “a to b.” For example, the scale 1 cm:3 ft is read “one centimeter to three feet.”
Reading Math

5. Course 3
7-7
Scale Drawings
Additional Example 1A: Using Proportions to Find Unknown Scales or Lengths
A. The length of an object on a scale drawing is 2 cm, and its actual length is 8 m. The scale is 1 cm: __ m. What is the scale?
1 cm
x m
2 cm
8 m
Set up proportion using
scale length .
actual length =
1  8 = x  2
Find the cross products.
8 = 2x
4 = x
Solve the proportion.
The scale is 1 cm:4 m.

6. Course 3
7-7
Scale Drawings
Additional Example 1B: Using Proportions to Find Unknown Scales or Lengths
B. The length of an object on a scale drawing is 1.5 inches. The scale is 1 in:6 ft. What is the actual length of the object?
1 in.
6 ft
1.5 in.
x ft
Set up proportion using
scale length .
actual length =
1  x = 6  1.5
Find the cross products.
x = 9
Solve the proportion.
The actual length is 9 ft.

7. 7-7 Scale Drawings Try This: Example 1A
Course 3
7-7
Scale Drawings
Try This: Example 1A
A. The length of an object on a scale drawing is 4 cm, and its actual length is 12 m. The scale is 1 cm: __ m. What is the scale?
1 cm
x m
4 cm
12 m
Set up proportion using
scale length .
actual length =
1  12 = x  4
Find the cross products.
12 = 4x
3 = x
Solve the proportion.
The scale is 1 cm:3 m.

8. 7-7 Scale Drawings Try This: Example 1B
Course 3
7-7
Scale Drawings
Try This: Example 1B
B. The length of an object on a scale drawing is 2 inches. The scale is 1 in:4 ft. What is the actual length of the object?
1 in.
4 ft
2 in.
x ft
Set up proportion using
scale length .
actual length =
1  x = 4  2
Find the cross products.
x = 8
Solve the proportion.
The actual length is 8 ft.

9. Insert Lesson Title Here
Course 3
7-7
Scale Drawings
Insert Lesson Title Here
A scale drawing that is smaller than the actual object is called a reduction. A scale drawing can also be larger than the object. In this case, the drawing is referred to as an enlargement.

10. Additional Example 2: Life Sciences Application
Course 3
7-7
Scale Drawings
Additional Example 2: Life Sciences Application
Under a 1000:1 microscope view, an amoeba appears to have a length of 8 mm. What is its actual length?
1000 1 =
8 mm
x mm
scale length
actual length
1000  x = 1  8
Find the cross products.
x = 0.008
Solve the proportion.
The actual length of the amoeba is mm.

11. 7-7 Scale Drawings Try This: Example 2
Course 3
7-7
Scale Drawings
Try This: Example 2
Under a 10,000:1 microscope view, a fiber appears to have length of 1mm. What is its actual length?
10,000 1 =
1 mm
x mm
scale length
actual length
10,000  x = 1  1
Find the cross products.
x =
Solve the proportion.
The actual length of the fiber is mm.

12. Insert Lesson Title Here
Course 3
7-7
Scale Drawings
Insert Lesson Title Here
A drawing that uses the scale in. = 1 ft is said to be in in. scale. Similarly, a drawing that uses the scale in. = 1 ft is in in. scale.
1 4
1 2

13. Additional Example 3A: Using Scales and Scale Drawings to Find Heights
Course 3
7-7
Scale Drawings
Additional Example 3A: Using Scales and Scale Drawings to Find Heights
A. If a wall in a in. scale drawing is 4 in. tall, how tall is the actual wall? 1 4
0.25 in.
1 ft =
4 in.
x ft.
scale length
actual length
Length ratios are equal.
Find the cross products.
0.25  x = 1  4
Solve the proportion.
x = 16
The wall is 16 ft tall.

14. Additional Example 3B: Using Scales and Scale Drawings to Find Heights
Course 3
7-7
Scale Drawings
Additional Example 3B: Using Scales and Scale Drawings to Find Heights 1 2
B. How tall is the wall if a in. scale is used?
0.5 in.
1 ft =
4 in.
x ft.
scale length
actual length
Length ratios are equal.
Find the cross products.
0.5  x = 1  4
Solve the proportion.
x = 8
The wall is 8 ft tall.

15. 7-7 Scale Drawings Try This: Example 3A
Course 3
7-7
Scale Drawings
Try This: Example 3A
A. If a wall in a in. scale drawing is 0.5 in. thick, how thick is the actual wall? 1 4
0.25 in.
1 ft =
0.5 in.
x ft.
scale length
actual length
Length ratios are equal.
Find the cross products.
0.25  x = 1  0.5
Solve the proportion.
x = 2
The wall is 2 ft thick.

16. Try This: Example 3A Continued
Course 3
7-7
Scale Drawings
Try This: Example 3A Continued 1 2
B. How thick is the wall if a in. scale is used?
0.5 in.
1 ft =
x ft.
scale length
actual length
Length ratios are equal.
Find the cross products.
0.5  x = 1  0.5
Solve the proportion.
x = 1
The wall is 1 ft thick.

17. Insert Lesson Title Here
Course 3
7-7
Scale Drawings
Insert Lesson Title Here
Lesson Quiz
1. What is the scale of a drawing in which a 9 ft wall is 6 cm long?
2. Using a in. = 1 ft scale, how long would a drawing of a 22 ft car be?
3. The height of a person on a scale drawing is 4.5 in. The scale is 1:16. What is the actual height of the person?
The scale of a map is 1 in. = 21 mi. Find each length on the map.
mi mi
1 cm = 1.5 ft 1 4
5.5 in.
72 in.
7 in.
0.25 in.