circumference of a circle

Front

What is the formula for the circumference of a circle?

Back

C = πd or C = 2πr, where C is the circumference, d is the diameter, and r is the radius.

Front

If the diameter of a circle is 21 feet, what is the circumference?

Back

C = πd = π(21) ≈ 65.94 feet.

Front

How do you calculate the diameter if you know the radius?

Back

Diameter (d) = 2 × Radius (r).

Front

What is the relationship between diameter and radius?

Back

The diameter is twice the length of the radius.

Front

If a circle has a radius of 10 feet, what is its diameter?

Back

Diameter = 2 × 10 ft = 20 ft.

Front

What is the circumference of a circle with a diameter of 15 millimeters?

Back

C = πd = π(15) mm.

Front

What is the radius of a circle with a diameter of 27 inches?

Back

Radius = Diameter / 2 = 27 in / 2 = 13.5 in.

Front

What does the term 'circumference' refer to?

Back

Circumference is the distance around the edge of a circle.

Front

How can you express the circumference in terms of radius?

Back

C = 2πr.

Front

What is the circumference of a circle with a radius of 5 cm?

Back

C = 2π(5) cm = 10π cm.