Section 1.7

Recall that perimeter is the distance around a figure, circumference is the distance around a circle, and area is the amount of surface covered by a figure.

Perimeter and circumference are measured in units of length.

Area is measured in square units.

Formulas for Perimeter P, Area A, and Circumference C

1. Square with side s

P = 4s

A = s2

2. Rectangle with length l and width w

P = 2l + 2w

A = lw

3. Triangle with side lengths a, b, and c, base b and height h

P = a + b + c

4. Circle. with diameter d and radius r

P = d = 2rA = r2

1

2A bh

The in-bounds portion of a singles tennis court is shown. Find its perimeter and area.

P = 2l + 2w A = l w= 2(78) + 2(27) = (78)(27)

= 156 + 54= 2106 ft2

= 210 ft.

Example 1

The smallest circle on an Olympic target is 12 centimeters in diameter. Find the circumference and area of the smallest circle to two decimal places. Use = 3.14.

C = d A = r2

= (3.14)(12) = (3.14)(62)

= 37.68 cm = (3.14)(36)

= 113.04 cm2

Example 2

Triangle JKL has vertices J(1, 6), K(6, 6) and L(3, 2). Find the perimeter of triangle JKL.

Example 3

1 2 3 4 5 6 7 8

1

2

3

4

5

6

7

8

J K

L

5JK

2 21 3 6 2JL

4 16

20

2 26 3 6 2KL

9 16 5

5 20 5P

10 20

The base of a triangle is 24 feet. Its area is 216 square feet. Find the height of the triangle.

Example 4

1

2A bh

1216 24

2h

216 12h

18 ft.h