Circles: Vocab and Circumference

Front

What is the radius of a circle?

Back

The radius is the distance from the center of the circle to any point on its circumference.

Front

What is the diameter of a circle?

Back

The diameter is the distance across the circle through its center, equal to twice the radius.

Front

If the diameter of a circle is 40 ft, what is the radius?

Back

20 ft (Radius = Diameter / 2).

Front

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

Back

C = 2 x pi x r.

Front

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

Back

C = pi x D.

Front

What is pi (π)?

Back

Pi (π) is a mathematical constant approximately equal to 3.14, representing the ratio of the circumference of a circle to its diameter.

Front

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

Back

Diameter = 2 x Radius.

Front

What is the relationship between radius and diameter?

Back

The diameter is always twice the length of the radius.

Front

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

Back

20 cm (Diameter = 2 x 10 cm).

Front

What is the circumference of a circle with a diameter of 16 cm?

Back

C = pi x 16 cm ≈ 50.27 cm.