1. 9-7
Perimeter
Course 1
Warm Up
Problem of the Day
Lesson Presentation

2. Course 1
9-7
Perimeter
Warm Up
1. What figure has four equal sides and four right angles?
2. What figure has eight sides?
3. What figure has five sides?
square
octagon
pentagon

3. 9-7 Perimeter Problem of the Day
Course 1
9-7
Perimeter
Problem of the Day
Find the greatest perimeter possible when 6 identical unit squares are arranged to form a closed figure. Adjacent squares must share an entire side.
14 units

4. Course 1
9-7
Perimeter
Learn to find the perimeter and missing side lengths of a polygon.

5. Insert Lesson Title Here
Course 1
9-7
Perimeter
Insert Lesson Title Here
Vocabulary
perimeter

6. Course 1
9-7
Perimeter
The perimeter of a figure is the distance around it. To find the perimeter you can add the lengths of the sides.

7. Additional Example 1: Finding the Perimeter of a Polygon
Course 1
9-7
Perimeter
Additional Example 1: Finding the Perimeter of a Polygon
Find the perimeter of the figure.
Add all the side lengths.
The perimeter is 17.2 in.

8. 9-7 Perimeter Check It Out: Example 1
Course 1
9-7
Perimeter
Check It Out: Example 1
Find the perimeter of the figure.
3.3 in.
3.3 in.
Add all the side lengths.
The perimeter is 18 in.
4.2 in.
4.2 in.
3 in.

9. Course 1
9-7
Perimeter

10. Additional Example 2: Using a Formula to Find Perimeter
Course 1
9-7
Perimeter
Additional Example 2: Using a Formula to Find Perimeter
Find the perimeter P of the rectangle.
12 cm
3 cm
P = 2l+ 2w
Substitute 12 for l and 3 for w.
P = (2 • 12) + (2 • 3)
P =
Multiply.
P = 30
Add.
The perimeter is 30 cm.

11. 9-7 Perimeter Check It Out: Example 2
Course 1
9-7
Perimeter
Check It Out: Example 2
Find the perimeter P of the rectangle.
15 cm
2 cm
P = 2l + 2w
Substitute 15 for l and 2 for w.
P = (2 • 15) + (2 • 2)
P =
Multiply.
P = 34
Add.
The perimeter is 34 cm.

12. Course 1
9-7
Perimeter
Additional Example 3A: Finding Unknown Side Lengths and the Perimeter of a Polygon
Find each unknown measure.
What is the length of side a if the perimeter equals 1,471 mm?
P = sum of side lengths
1,471 = a
Use the values you know.
1,471 = 1,178 + a
Add the known lengths.
1,471 – 1,178 = 1,178 + a – 1,178
Subtract 1,178 from both sides.
293 = a
Side a is 293 mm long.

13. Course 1
9-7
Perimeter
Additional Example 3B: Finding Unknown Side Lengths and the Perimeter of a Polygon
Find each unknown measure.
What is the perimeter of the polygon?
First find the unknown side length.
72 cm
Find the sides opposite side b.
The length of side b =
Side b is 72 cm long.
P =
Find the perimeter.
P = 254
The perimeter of the polygon is 254 cm.

14. Course 1
9-7
Perimeter
Additional Example 3C: Finding Unknown Side Lengths and the Perimeter of a Polygon
The width of a rectangle is 19 cm. What is the perimeter of the rectangle if the length is 4 times the width? 4w
19 cm
l = 4w
Find the length.
l = (4 • 19)
Substitute 19 for w.
l = 76
Multiply.

15. Additional Example 3C Continued
Course 1
9-7
Perimeter
Additional Example 3C Continued 4w
19 cm
Use the formula for the perimeter of a rectangle.
P = 2l + 2w
Substitute 76 and 19.
P = 2(76) + 2 (19)
P =
Multiply.
P = 190
Add.
The perimeter of the rectangle is 190 cm.

16. 9-7 Perimeter Check It Out: Example 3A Find each unknown measure.
Course 1
9-7
Perimeter
Check It Out: Example 3A
Find each unknown measure.
What is the length of side a if the perimeter equals 1,302 mm?
212 mm
280 mm
250 mm a
P = sum of side lengths
240 mm
1,302 = a
Use the values you know.
1,302 = a
Add the known lengths.
1,302 – 982 = a – 982
Subtract 982 from both sides.
320 = a
Side a is 320 mm long.

17. 9-7 Perimeter Check It Out: Example 3B Find each unknown measure.
Course 1
9-7
Perimeter
Check It Out: Example 3B
Find each unknown measure.
What is the perimeter of the polygon?
12 m
8 m
First find the unknown side length.
14 m
4 m
Find the sides opposite side b.
6 m
The length of side b =
16 m
b m
Side b is 16 m long.
P =
Find the perimeter.
P = 60
The perimeter of the polygon is 60 m.

18. 9-7 Perimeter Check It Out: Example 3C
Course 1
9-7
Perimeter
Check It Out: Example 3C
The width of a rectangle is 13 cm. What is the perimeter of the rectangle if the length is 5 times the width? 5w
13 cm
l = 5w
Find the length.
l = (5 • 13)
Substitute 13 for w.
l = 65
Multiply.

19. Check It Out: Example 3C Continued
Course 1
9-7
Perimeter
Check It Out: Example 3C Continued
65 cm
13 cm
Use the formula for the perimeter of a rectangle.
P = 2l + 2w
Substitute 65 and 13.
P = 2(65) + 2 (13)
P =
Multiply.
P = 156
Add.
The perimeter of the rectangle is 156 cm.

20. Insert Lesson Title Here
Course 1
9-7
Perimeter
Insert Lesson Title Here
Lesson Quiz: Part I
Find each perimeter.
3. What is the perimeter of a polygon with side lengths of 15 cm, 18 cm, 21 cm, 32 cm, and 26 cm?
9 cm 5 6 __
4 ft
112 cm

21. Insert Lesson Title Here
Course 1
9-7
Perimeter
Insert Lesson Title Here
Lesson Quiz: Part II
4. What is the perimeter of a rectangle with length 22 cm and width 8 cm?
5. The width of a rectangle is 12 in. What is the perimeter of the rectangle if the length is 7 in. longer than the width?
60 cm
62 in.

22. Find the perimeter of the shape below

23. P= 70 mm