Warm Up

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Warm Up
Problem of the Day
Lesson Presentation
Lesson Quizzes
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Warm Up Add or multiply. 1. 8.2 5.6 8.2
5.6 2. 12.4 15.8 9.3 3. 22 3.14
27.6
37.5
69.08
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Problem of the Day A rectangular piece of sheet
metal measures 5 in. by 6 in. A rectangular notch
1 in. deep and in. wide is cut
7 64
out of the middle of each side. What is the
perimeter of the piece after the cuts have been
made? (Hint You dont have to use fractions.)
30 in. (22 in. plus 8 in. for the eight 1 in.
cuts)
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Sunshine State Standards
Prep for MA.7.G.2.1 Justify and use formulas for
surface areaof pyramids, prisms, cylinders, and
cones. Review of MA.6.G.4.1
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Vocabulary
perimeter circumference pi
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Perimeter is the distance around a geometric
figure. To find the perimeter P of a polygon, you
can add the lengths of its sides.
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Additional Example 1 Finding the Perimeter of a
Polygon
Find the perimeter.
25 cm
25 cm
15 cm
P 25 25 15
Use the side lengths.
P 65
Add.
The perimeter of the triangle is 65 cm.
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Check It Out Example 1
Find the perimeter of the polygon.
20 cm
25 cm
30 cm
P 25 20 30
Use the side lengths.
P 75
Add.
The perimeter of the triangle is 75 cm.
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Additional Example 2 Using Properties of a
Rectangle to Find Perimeter
Find the perimeter of a rectangle.
14 ft
18 ft
P 2l 2w
Use the formula.
P (2 18) (2 14)
Substitute for l and w.
P 36 28
Multiply.
P 64
Add.
The perimeter of the rectangle is 64 ft.
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Check It Out Example 2
Find the perimeter of a rectangle.
16 ft
8 ft
P 2l 2w
Use the formula.
P (2 16) (2 8)
Substitute for l and w.
P 32 16
Multiply.
P 48
Add.
The perimeter of the rectangle is 48 ft.
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Additional Example 3A Finding the Circumference
of a Circle
Find the circumference of the circle to the
nearest tenth. Use 3.14 for ?.
C ?d
You know the diameter.
12 in.
C ? 3.14 12
Substitute for ? and d.
C ? 37.68
Multiply.
The circumference of the circle is about 37.7 in.
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Additional Example 3B Finding the Circumference
of a Circle
Find the circumference of the circle to the
nearest tenth. Use 3.14 for ?.
C 2?r
You know the radius.
18 cm
C ? 2 3.14 18
Substitute for ? and r.
C ? 113.04
Multiply.
The circumference of the circle is about 113.0 cm.
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Check It Out Example 3A
Find the circumference of the circle to the
nearest tenth. Use 3.14 for ?.
C ?d
You know the diameter.
7 in.
C ? 3.14 7
Substitute for ? and d.
C ? 21.98
Multiply.
The circumference of the circle is about 22.0 in.
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Check It Out Example 3B
Find the circumference of the circle to the
nearest tenth. Use 3.14 for ?.
C 2?r
You know the radius.
11 cm
C ? 2 3.14 11
Substitute for ? and r.
C ? 69.08
Multiply.
The circumference of the circle is about 69.1 cm.
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Additional Example 4 Application
The diameter of a circular pond is 42 m. What is
its circumference? Use
for ?.
22 7
C ?d
You know the diameter.
22 7
22 7
42
Substitute
for ? and 42 for d.
C ?
22 7
42 1
Write 42 as a fraction.
C ?

6
22 7
42 1

Simplify.
C ?
1
C ? 132
Multiply.
The circumference of the pond is about 132 m.
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Check It Out Example 4
The diameter of a circular spa is 14 m. What is
its circumference? Use
for ?.
22 7
C ?d
You know the diameter.
22 7
22 7
14
Substitute
for ? and 14 for d.
C ?
22 7
14 1
Write 14 as a fraction.
C ?

2
22 7
14 1

Simplify.
C ?
1
C ? 44
Multiply.
The circumference of the spa is about 44 m.
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Lesson Quizzes
Standard Lesson Quiz
Lesson Quiz for Student Response Systems
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Lesson Quiz

• Find the perimeter.
• 1. 2. a 10 in. by 8 in. rectangle
• 3. What is the circumference of a circle with a
• a radius of 8 inches? Use 3.14 for ?.
• 4. If a guardrail is to be placed around the edge
• of a circular swimming pool with a diameter
  of
• 21 ft, how many feet of railing will be
  needed?

36 in.
45 m
50.24 in.
22 7
66 ft
Use for ?.
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Lesson Quiz for Student Response Systems

• 1. Identify the perimeter.
• A. 10 in.
• B. 15 in.
• C. 24 in.
• D. 48 in.

6 in.
6 in.
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Lesson Quiz for Student Response Systems

• 2. Identify the perimeter.
• A. 52 m
• B. 82.5 m
• C. 165 m
• D. 330 m

18 m
8 m
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Lesson Quiz for Student Response Systems

• 3. What is the circumference of a circle with a
  radius of 13 in.? Use 3.14 for ?.
• A. 40.82 in.
• B. 81.64 in.
• C. 265.33 in.
• D. 530.66 in.

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Lesson Quiz for Student Response Systems

• 4. Jill plans to build a fence around her
  circular garden. About how many feet of fencing
  would be required if the garden has a diameter of
  28 ft?
• A. 88 ft
• B. 66 ft
• C. 44 ft
• D. 22 ft