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 Parallelogram

Let'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 ft

How 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 cm2.2 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 ft10 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 Triangle

Let'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 2

20 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 r

2

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?