Fill in the number of sides

1
Fill in the number of sides
Find the sum of the measures of the interior
angles of a Nonagon.
Polygon Name Number of Sides
Triangle
Heptagon
Nonagon
Hexagon
Pentagon
Dodecagon
Quadrilateral
Decagon
Octagon
3
7
9
6
5
(9 2)180 7(180) 1,2600
12
4
10
8
03/12/08
2
Ch. 7-6 Areas of Polygons
Area is the number of square units the figure
encloses. It is flat 2 dimensional
cm2 Example If you were ordering carpet for a
rectangular room, you would need to know the area
of the room.
Important Formulas for finding area Parallelogram
A bh where b is the base and h is the
height Triangle A 1/2bh where b is the base
and h is the height Trapezoid A 1/2h(b1 b2)
3
Example 1 Find the area of each figures below.
Use the appropriate formula.
Area of a Triangle ½ bh The base is 7 and the
height is 3.
6 cm.
3 cm.
7 cm.
A ½ (7)(3) 10.5 cm.2
Area of a Parallelogram bh The base is 12 and
the height is 20.
22 cm.
20 cm.
A (12)(20) 240 cm.2
12 cm.
4
Example 2 Find the area of each figure below.
Use the appropriate formula.
6 m.
Area of a Trapezoid ½h(b1 b2) The bases are 6
and 3 and the height is 4.
4 m.
A ½ (4)(3 6) 18 m.2
3 m.
Example 3 Use the area formulas to solve for
each unknown below. a.) The area of a
parallelogram is 221 yd.2 Its height is 13 yd.
What is the length of its corresponding base?
Use the Area formula for a parallelogram, plug in
what you know and solve for the unknown.
221 13b Divide both sides by 13 b 17 yd.
5
b.) A triangle has area 85 cm.2 Its base is 5
cm. What is its height?
Use the Area formula for a triangle, plug in what
you know and solve for the unknown.
85 ½(5)h Multiply 5 1/2 85 5/2h Divide by
5/2, since it is a fraction you are really
multiplying by the reciprocal! 2/5 85 5/2h
x 2/5 34 cm. h
6
Ch. 7-7 Circumference and Area of a Circle
Important formulas when dealing with
circles Circumference diameter multiplied by
pi or 3.14 C Circumference 2 multiplied by
the radius multiplied by pi or 3.14 C Area of
a Circle pi multiplied by the radius squared A

Chord
Parts of a Circle
Radius
Circumference
Diameter
7
Example 1 Find the circumference and area of
each object below. Use the formulas given.
Find the circumference and area of the basketball
hoop
C 45 3.14 141.3 cm.
45 cm.
A 3.14 (22.5)2 1589.6 cm.2
Find the circumference and area of the tire
C 12 3.14 37.68 in.
A 3.14 (6)2 113.04 in.2
12 in.
8
Example 2 Find the area of each irregular figure
below. You are going to have to use multiple
area formulas.
First find the area of the rectangle. A length
multiplied by width
10 in.
Area of the rectangle 7 10 70 in. 2
7 in.
Next find the area of the semi-circle A
Area of Semi-Circle ½ (3.14)(5)2 39.25 in.2
Last, add the two areas together 39.25 70
109.25 in.2
9
Example 3 Find the area of each irregular figure
below. You are going to have to use multiple
area formulas.
6.6 m.
13.2 m.
First find the area of the rectangle. A length
multiplied by width
19.8 m.
Area of the rectangle 19.8 13.2 261.36 m. 2
Next find the area of the semi-circle A
Area of Semi-Circle ½ (3.14)(6.6)2 68.39 m.2
Last need to subtract the area of the semi-circle
from the area of the rectangle 261.36
68.39 192.97 m.2
10
HW Pg. 331

• PG 331 1-4 all, 6-10 even
• PG 338 4-22 even