Pre-Algebra Demystified

EXAMPLE

Find the area of the trapezoid shown in Fig. 9-14.

SOLUTION

A¼

1

2

hðb 1 þb 2 Þ

¼

1

2

5ftð3 ft+2 ftÞ

¼

1

2

5ft5ft

¼ 12 :5ft^2

The area of a circle can be found by using the formulaA¼r^2 , where

¼ 3 :14 and r is the radius.

EXAMPLE

Find the area of the circle shown in Fig. 9-15. Usep¼ 3 : 14 :

174 CHAPTER 9 Informal Geometry

Fig. 9-15.

Fig. 9-14.