This document defines perimeter, circumference, and area of different shapes. It provides the following definitions: Perimeter is the distance around a geometric figure. Circumference is the distance around a circle, which is calculated by multiplying the diameter by pi. The area of a rectangle is calculated by multiplying its length by its width. The area of a triangle is half the product of its base and height. The area of a circle is calculated by multiplying pi by the square of the radius. Examples are given for calculating each measurement.

1. Perimeter, Circumference
and Area
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2. Perimeter and Circumference
 Perimeter : The distance around a geometric
figure.
 Circumference: The distance around a circle.

3. Perimeter
 To find perimeter add the lengths of all the
sides.
– Example: Find the perimeter of the polygon
8 in
6 in
8 in
6 in
P = 8 + 8 + 6 + 6
P = 28
The perimeter is 28 in

4. Perimeter
– Example : Find the perimeter of the triangle
12 in
12 in
16 in
P = 12 + 12 + 16
P = 40
The perimeter is 40 in

5. Your Turn…. Find the perimeter
 pg. 426 #1-3 ( 3 minutes)
 Make sure that there are no naked numbers.
1. P = 6 + 4 + 8
P = 18m
2. P = 7 + 5 + 5 + 7
P = 24in
3. P = 8 + 8 + 8 + 8
P = 32 ft

6. Circumference
 To find the circumference multiply times
diameter, where is 3.14
C = d
Diameter
π
π
π

7. Definitions
 Diameter (d): a line that passes through the
center of a circle
 Radius (r): half the diameter
 d = 20, then r = 10
 r = 15, then d = 30

8. Circumference
 Example: Find the
circumference
Diameter = 8 in
Circumference = d
C = 3.14(8)
C = 25.12
The circumference is 25.12 in
π

9. Circumference
Example: Find the circumference
radius = 10 cm
Circumference = d
Diameter = 2r = 2 (10) = 20
C = 3.14(20)
C = 62.8
The circumference is 62.8 cm
π

10. Your Turn…. Find the circumference
 pg. 426 # 7-9
 No naked numbers.
7. C = d 8. C = d
C = 3.14(12) C = 3.14(3)
C = 37.7m C = 9.4 ft
9. C = d
C = 3.14 (16)
C = 50. 2 in
π π
π

11. Area of Rectangles
 The area of a rectangle is the product of its length
and width.
A = ω
ω


12. Area of Rectangles
 Find the area of the rectangle
10 ft
7.5 in
A = ω
A = 10(7.5)
A = 75 ft²
The area is 75 ft²


13. Area of Triangles
 The area of a triangle is half the product of its
base b and its height h.
A = bh
height
base
2
1

14. Area of Triangles
 Example: Find the area of the triangle
2
1
6 in
5 in
A = bh
A = 5(6)
A = 15 in²
2
1

15. Area of Circles
 The area of a circle is the product of and the
square of the circle’s radius r.
A = r²
radius
π
π

16. Area of Circles
 Example: Find the area
of the circle
r = 3 m
A = r²
A = 3.14(3)²
A = 3.14(9)
A = 28.26 m²
The area of the circle is
28.26m²
π

17. Area of Circles
d = 8 in
A = r²
Radius = 4 in
A = 3.14(4)²
A = 3.14(16)
A = 50.24 in²
The area of the
circle is 50.24in²
π

18. Lets Review
 Perimeter = Sum of all sides
 Circumference = d
 Area of a Rectangle = ω
 Area of a Triangle = bh
 Area of a Circle = r²
π

2
1
π