Circumference of a Circle

Is the red line a radius or diameter of the circle?

• Radius
• Diameter

If my diameter is 19 inches, what is my radius?

• 38 inches
• 9.5 inches
• 59.66 inches
• 119.32 inches

What is the radius?

• 18
• 72
• 38
• 14

What is the circumference of this circle ?

• 3.14 cm 
• 37.68 cm
• 24 cm
• 68.4 cm

Find the circumference (to the nearest whole number)

• 88 in
• 44 in
• 116 square in
• None of the above

What is the formula for circumference of a circle given the diameter?

• C = pi x r
• C = pi x 2r
• C = pi x D
• C = pi x 2D

A Circle has a radius of 4.  What is the circumference of the circle? (Best Choice)

• 4π or about 12.56
• 16π or about 50.24
• 2π or about 6.28
• 8π or about 25.12

A Circle has a radius of 6 inches.  What is the circumference of the circle? (Best Choice)

• 3π or about 9.42 in
• 6π or about 18.84 in
• 12π or about 37.68 in
• 36π or about 113.04 in 

A Circle has a diameter of 10 centimeters.  What is the circumference of the circle? (Best Choice)

• 5π or about 15.7 cm
• 10π or about 31.4 cm
• 20π or about 62.8 cm
• 100π or about 314 cm 

A circular window has a diameter of 24 inches.  A piece of metal is to go around the window for a frame. How long does the metal need to be? (Best Choice)

• 24π or about 75.36 in
• 12π or about 37.68 
• 576π or about 1,808.64 in
• 144π or about 452.16 in