Circles

Radius and Diameter

100

A radius of 6 mm -- what is diameter?

12 mm

200

A diameter of 15.5 in--what is radius

7.75 in

300

A radius of 0.25 m --what is diameter

0.5 m

400

A radius of x feet--what is the diameter?

2x

500

A diameter of 25b--what is radius?

12.5b

Circumference

100

What is the formula for circumference when you have radius or are looking for the radius?

C = 2(pi)r

200

What is the formula for circumference that involves diameter

C = (pi)d

300

What is pi? (Answer is NOT 3.14)

Ratio of circumference to diameter

400

What is circumference of a circle with a radius of 12 feet?

75.36 ft

500

If a circumference of a circle is 100 inches, what is the diameter? Round to the second decimal place. 

31.85 inches

Area

100

If the radius of a circle is 5.5 cm, what is the area? Round to two decimal places.

94.99 cm²

200

If the diameter of a circle is 25 mm, what is the area? Round to two decimal places.

490.63 mm²

300

If the area of a round table is 200.96 square feet, what is the radius of the table?

8 ft

400

Area of a circle = 314 ft²

What is the diameter?

D = 20 ft

500

What is the area of a semi-circle with a diameter of 14 inches?

76.93 in²

Word Problems

100

A round swimming pool is 12 feet from one side to the other. What is the circumference?

37.68 ft

200

A horse is tethered to a post in the middle of a fenced area with a lead that is 10 feet long. How much area does the horse have to wander around in?

314 ft²

300

A table has a distance around it of 150.72 inches. What is the table's diameter?

48 inches

400

They want to frost the top of a cake and wonder how much frosting they will need. If the diameter of the cake is 22 cm, how much area will the frosting need to cover?

379.94 cm²

500

The area of a circular paved lot is 530.66 yds²

What is the distance around the edge of the paved lot?

81.64 yds

Mixed Problems

100

What is the radius of a circle if the circumference is 100 m? Round to two places. 

15.92 m

200

What is the radius of a circle with an area of 706.5 cm²

15 cm

300

What is the difference in area between a circle with a 10 ft radius and a circle with a 20 ft radius?

942 ft²

400

What is the area of a circle that has a circumference of 56.52 km?

254.34 km²

500

If a circle is just enclosed inside a square that has side length = 10 ft, what is the area outside the circle and inside the square?

21.5 ft²