Post on 23-Feb-2016
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Area of Rectangles
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Area - The number of square units (units2) it takes to
cover the surface of a figure.
ALWAYS label units2!!!
How many 1 ft2 tiles does it take to cover the rectangle?
Use the squares to find out!
Look for a faster way than covering the whole figure.
12 ft
6 ft
A = length(width)A = lw
A = side(side)A = s2
The Area (A) of a rectangle is found by using the formula:
The Area (A) of a square is found by using the formula:
65 What is the Area (A) of the figure?
15 ft
6 ft
66 Find the area of the figure below.
7
67 Dr. Dan wants to keep his kitten from running through his flower bed by putting up some fencing. The flower bed is 10 ft. by 6ft. Will Dr. Dan need to know the area or the perimeter of his flower bed to keep his kitty from trampling the flowers?
A Area
B Perimeter
68 Now solve the problem....
Dr. Dan wants to keep his kitten from running through his flower bed by putting up some fencing. The flower bed is 10 ft. by 6ft. How much fencing will he need?
Area of Parallelograms
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Area of a ParallelogramLet's use the same process as we did for the rectangle. How many 1 ft2 tiles fit across the bottom of the parallelogram?
Area of a Parallelogram.Let's use the same process as we did for the rectangle. If we build the parallelogram with rows of 14 ft2, what happens?
How tall is the parallelogram?How can you tell?
14 ft
How does this help us find the area of the parallelogram?
14 ftHow do you find the area of a parallelogram?
4 ft
A = base(height)A = bh
The Area (A) of a parallelogram is found by using the formula:
Note: The base & height always form a right angle!
Example.
Find the area of the figure.4 cm
4 cm
2.2 cm 2.2 cm1.9 cm
click to reveal
4
Try These.
Find the area of the figures.
8
75
click to reveal
11 m
click to reveal
14 m
11 m
20 m
69 Find the area.
11 ft 10 ft
12 ft
70 Find the area.
17 in
17 in
10 in 12 in12 in
71 Find the area.
7 m
13 m 13 m
7 m
11 m
72 Find the area.
Area of Triangles
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Area of a TriangleLet's use the same process as we did for the rectangle & parallelogram. How many 1 ft2 tiles fit across the bottom of the triangle?
Area of a Triangle
If we continue to build the triangle with rows of 10 ft2, what happens?
How tall is the triangle? How can you tell?
10 ft
How does this help us find the area of the triangle?
Find the area of the rectangle, then divide by 220 ft2
See that the rectangle we built is twice as large as the triangle. How do you find the area of a triangle?
10 ft
4 ft
Is this true for all triangles?Let's see!
Calculating base(height) results in 2 triangles!
The Area (A) of a triangle is found by using the formula:
Note: The base & height always form a right angle!
Example.
Find the area of the figure.4 cm
10 cm 10 cm
6 cmclick to reveal
Try These.
Find the area of the figures.
13 ft
11 ft
9 ft 12 ft 1420
16
15
click to reveal click to
reveal
73 Find the area.
8 in
5 in
11 in 10 in
74 Find the area
15 m
8 m9 m 12 m
Area of Trapezoids
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Area of a Trapezoid
·Cut the trapezoid in half horizontally·Rotate the top half so it lies next to the bottom half·A parallelogram is created
See the diagrams belowBase1
Base2
Height
Base1Base2
The Area (A) of a trapezoid is found by using the formula:
Note: The base & height always form a right angle!
Example.
Find the area of the figure.
12 cm
10 cm 11 cm
9 cm
click to reveal
Try These.
Find the area of the figures.13 ft
11 ft
9 ft 11 ft
20
15
click to reveal
11 ft
click to reveal
9 117
75 Find the area of the trapezoid.
4 m
10 m
6.5 m
76 Find the area of the trapezoid.
22 cm
14 cm
8 cm
Area of Circles
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Area of a Circle
The Area (A) of a Circle is found by solving the following formula:
7 cm
Find the area of the circle.A = π r2
1. Substitute the radius into formula.A = π (7)2
2. Use 3.14 as an approximation for π.A = 3.14(49)A = 153.86 cm2
3. Don't forget to label the units as square units.
77 What is the Area (A) of a Circle with a radius (r) of 8 m?
8 m
78 What is the Area (A) of the circle?
79 What is the Area (A) of the circle?
80 A circular sprinkler sprays water with a radius of 11 ft. How much area can the sprinkler cover?
81 What is the area of a circle with a diameter of 24 yds?
82 What is the radius of a circle whose area is 254.34 mm2?
83 A circular pool has an area of 153.86 ft2.What is its diameter?