Pre-Algebra Demystified

4. Find the circumference of a circle whose diameter is 12 inches. Use
   p¼ 3 :14.


5. Find the circumference of a circle whose radius is 30 feet. Use
   p¼ 3 :14.

ANSWERS

1. 28 feet


2. 12 yards


3. 88 inches


4. 37.68 inches


5. 188.4 feet

Area

Theareaof 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.

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 inch¼1 in.^2

 1 square foot¼1ft^2

 1 square yard¼1yd^2

 1 square mile¼1mi^2

The area of a rectangle is found by using the formula A¼lw, where l is the

length and w is the width.

EXAMPLE

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

170 CHAPTER 9 Informal Geometry

Fig. 9-7.