Circumferences and Areas of Circles

Which expression could be used to find the approximate circumference of the quilt piece?

• 2(pi)16

• 2(pi)8

• 2(8)

• 2(4)

Which best approximates the circumference of the outer ring of this clip?

• 27cm

• 18cm

• 9cm

• 3cm

What is the circumference?

• 48

• 96

• 24

• 18

What is the circumference?

• 36

• 18pi

• 108pi

• 36pi

Sort the problems into two groups based on whether you would use the circumference or the area of the circle to answer the question.

Groups:

(a) Circumference

,

(b) Area

• How much room is there to spread frosting on a cookie?

• How many feet are traveled by a person riding once around a merry-go-round?

• How much green space is there inside a traffic roundabout?

• How fast do you go when riding a Ferris Wheel?

• How much fabric is needed for a round table cloth?

• How many times must a horse go around a horse walker to walk 1 mile?

• How many square inches of cheese fit on a slice of pizza?

• How far does a unicycle move when the wheel makes 5 full rotations?

A dog is tied to a wooden stake in a backyard. His leash is 3 meters long and he runs around in circles pulling the leash as far as it can go. How much area does the dog have to run around in?

• 113.04 square meters

• 9.42 square meters

• 18.84 square meters

• 28.26 square meters

What is the formula to calculate the circumference of a circle?

How many cookies are there?

• 48 cookies

• 24 cookies

• 8 cookies

• 4 cookies

What is the diameter?

• 6.5

• 15

• 26

• 78

The distance around a circle; much like the perimeter of a rectangle.

• perimeter

• diameter

• circumference

• radius