2.8 – Circles. TermPictureFormula Circumference r = radius d = diameter.

2.8 – Circles

Term Picture Formula

Circumference2C r

C dr = radius

d = diameter

1. Find the circumference of the circle. Leave answer in terms of .

2C r 2 7C

14C cm

1. Find the circumference of the circle. Leave answer in terms of .

C d12C in12 in

2. Find the radius.

2C r24 2 r 2 2 12in r

3. Find the perimeter. Leave answers in terms of pi.

8

P = CircleTwo segments +15 15P 830 8P un

4. A bike wheel has a diameter of 16 inches. If the wheel revolves 7 times, how far does the bike move?

16in

C d16C x 7 times

112 in

Term Picture Formula

Area2A r

4. Find the area of the circle.

2A r 25A

25A 2cm

5. Find the area of the circle.

2A r 27A

49A 2in

7 7

6. Find the area of the shaded figure.

A Big little 2 2A R r

24A 2

216A 4

212A in

8 16A 232A

1024A 16 16

1024A 256

216 4

2cm

2A r264 r

264 r

8in r 16in d

8. You want to design a new backyard for your family. The design is a rectangle with a semicircle on one end.

a. Find the area of the backyard. Show all work.

1

2A

8 12A

96A 116

2

A 96 8

214

2

ft2

b. The backyard needs to be covered with grass. If the grass costs $3 per square foot, how much will it cost?

96A 8 ft2

96A 25.13121.13A

x $3

$363.39