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# Area of Squares, Rectangles and Triangles Help

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## Area of Squares, Rectangles, and Triangles

The area of a geometric figure is the number of square units contained in its surface. For example, the area of the 3-inch by 2-inch rectangle is 6 square inches as shown in Fig. 9-7 .

Fig. 9-7.

Area is measured in square units. A square inch is a square whose sides measure one inch. A square foot is a square whose sides measure one foot, etc. Square units are abbreviated using two for the exponent:

• 1 square inch = 1 in. 2
• 1 square foot = 1 ft 2
• 1 square yard = 1 yd 2
• 1 square mile = 1 mi 2

### Area of a Rectangle

The area of a rectangle is found by using the formula A = lw, where l is the length and w is the width.

#### Example 1

Find the area of the rectangle shown in Fig. 9-8 .

Fig. 9-8.

### Area of a Square

The area of a square can be found by using the formula A = s 2, where s is the length of its side.

#### Example 2

Find the area of the square shown in Fig. 9-9 .

Fig. 9-9.

### Area of a Triangle

To find the area of a triangle you need to know the measure of its altitude. The altitude of a triangle is the measure of a perpendicular line from its highest point to its base (the side opposite its highest point). See Fig. 9-10.

Fig. 9-10.

The area of a triangle can be found by using the formula , where b is the base and h is the height or altitude .

#### Example 3

Find the area of the triangle shown in Fig. 9-11 .

Fig. 9-11.

### Area of Squares, Rectangles, and Triangles Practice Problems

#### Practice

1. Find the area of a rectangle whose length is 123 yards and whose width is 53 yards.

2. Find the area of a square whose side is 53 inches.

3. Find the area of a triangle whose base is 16 inches and whose height is 9 inches.

1. 6519 yd 2

2. 2809 in. 2

3. 72 in. 2

Practice problems for these concepts can be found at: Informal Geometry Practice Test.

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