Diameter, Radius, Area and Circumference of a Circle

What is the circumference of a circle with a radius of 21 cm?

• 131.9 cm

• 121.9 cm

• 111.9 cm

• 141.9 cm

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

• Radius

• Diameter

What is the radius of this circle?

• 18

• 36

• 9

• 6

What is the radius of this circle?

• 12cm

• 6cm

• 24cm

• 3cm

What is circumference?

• The distance around a circle.

• The space inside the circle.

• A line from side to side passing through the center.

• A line from the center to the side.

Find the circumference of the circle

• 21.98

• 153.86

• 43.96

• 615.44

The radius is 8 inches.  What is the circumference?

• 50.24 inches

• 25.12 inches

• 12.56 inches

• 200.96 inches

What is the area of a circle?

• The distance around a circle.

• The space inside the circle.

• A line from side to side passing through the center.

• A line from the center to the side.

A Circle has a radius of 4.  What is the area of the circle? (Best Choice) (note: units are squared)

• 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 area of the circle? (Best Choice)

• 3π or about 9.42 in²

• 6π or about 18.84 in²

• 12π or about 37.68 in²

• 36π or about 113.04 in²