Area and Circumference of Circles

Diameter 32 inches
What is the radius?

• 16 inches

• 64 inches

• 96 inches
  96 inches

• 16 ft 

What formula is this used for:
πd

• Area

• Circumference 

• Surface Area

• Volume 

A DVD has a diameter of 15 millimeters. Which equation would help you determine the circumference?

• c = 15π

• C = 2π15

• c = 15 ÷ π

• c = 15 π

What formula is used to find the distance around a circle?

• Area

• Surface area

• Circumference

• Volume

A bicycle tire has a diameter of 20 inches. How many inches is one full revolution of the wheel?  

• 31.4 in

• 1256 in

• 125.6 in

• 62.8 in

Other than the formula C=πd what is another formula for circumference of a circle?

• C=2π

• C=2πr

• C=πr²

• C=πd²

If the problem ask you to find the distance around a circle, which formula should you use?

• r = 1/2d

• d = 2r

• C = πd

• A = πr²

Your Geometry teacher rents a fast car for the weekend. Her friend, a Physics teacher, uses a stopwatch to time how long it takes your teacher to make one complete revolution about the track. Is this question circumference or area?

• Circumference

• Area

Ray wants to build a fence around his circular garden outside. The garden has a radius of 6 ft. How many feet of fencing does he need?

• 37.68 ft

• 18.84 ft

• 113.04 ft

• 452.16 ft

Randy’s circular garden has a radius of 1.5 feet. He wants to enclose the garden edging that costs $0.75 per foot. About how much will the edging cost? Use 3.14 for π!

• $9.42

• $7.07

• $3.53

• $4.71