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PPT – Lesson 8 ~ The Concept of Area ~ Areas of Rectangles and Squares ~ Areas of Triangles ~ Areas of Circles ~ Areas of Parallelograms and Trapezoids PowerPoint presentation | free to download - id: 46356e-ZTVkY

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Lesson 8The Concept of AreaAreas of

Rectangles and SquaresAreas of

TrianglesAreas of CirclesAreas of

Parallelograms and Trapezoids

Example 8.1

Example 8.5

Example 8.2

Example 8.6

Lesson 8.B

Area ofRectangles and Squares

The area of a closed figure is the number of

square units contained in the figure.

4 units

2 units

Area of rectangle length x width

Area of square (length of a side)2

Lesson 8.BPage 2

Area ofRectangles and Squares

In algebra we use formulas to find the areas of

geometric shapes. The following formulas are

used for finding the areas of rectangles and

squares. Commit these to memory.

Area of a Rectangle

Area of a Square

Lesson 8.BPage 3

Area ofRectangles and Squares

Let us use the formulas to find the area of the

figures below.

6 units

3 units

3 units

3 units

Example 8.1

Area ofRectangles and Squares

Find the area of this figure. All angles are

right angles. Dimensions are in centimeters.

Use formulas.

2

4

A1

5

2

A2

Example 8.2

Area ofRectangles and Squares

Find the area of the shaded portion of this

figure. All angles are right angles. Dimensions

are in meters.

Use formulas.

6

2

8

A2

10

Lesson 8.3

Area ofTriangles

The altitude, or height, of a triangle is the

perpendicular distance from either the base of

the triangle or an extension of the base to the

opposite vertex.

h

h

h

b

Area of a Triangle

Commit this formula to memory.

Example 8.3

Area of Triangles

Find the area of these triangles. Dimensions are

in inches.

in2

Example 8.4

Area of Triangles

Find the area of this right triangle. Dimensions

are in feet.

8

6

10

ft2

Example 8.5

Area of Triangles

Find the area of this figure. Corners that look

square are square. Dimensions are in yards.

6

A1

4

A2

(6)

(4)

10

Example 8.6

Area of Circles

The radius of a circle is 3 centimeters. Find

the area of the circle.

Commit this formula to memory.

cm2

Example 8.7

Area of Circles

The area of a circle is 25 square meters. Find

the radius of the circle.

Example 8.8

Area of Circles

Find the area of this figure. Lines that look

parallel are parallel. Dimensions are in inches.

Area area of triangle area of rectangle

area of semicircle

5

2

4

2

5

7

( )

in

Example 8.9

Area of Parallelogramsand Trapezoids

Find the area of this figure. Lines that look

parallel are parallel. Dimensions are in inches.

? Commit this formula to memory.

Example 8.10

Area of Parallelogramsand Trapezoids

Find the area of this trapezoid. Dimensions are

in meters.

Commit this formula to memory.

9

5

5

5

15

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