Area and Circumference of Circles

Front

What is the formula for the circumference of a circle?

Back

Circumference = π × diameter or Circumference = 2 × π × radius.

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 a circle has a radius of 5 cm, what is its diameter?

Back

Diameter = 2 × radius = 2 × 5 cm = 10 cm.

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

How do you find the circumference of a circle if you know the radius?

Back

Circumference = 2 × π × radius.

Front

What is π (pi)?

Back

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

Front

If the circumference of a circle is 31.4 cm, what is the radius?

Back

Radius = Circumference / (2 × π) = 31.4 cm / (2 × 3.14) = 5 cm.

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 diameter of 18 meters, what is its radius?

Back

Radius = Diameter / 2 = 18 m / 2 = 9 m.

Front

What is the circumference of a circle with a diameter of 18 meters?

Back

Circumference = π × diameter = π × 18 m = 18π or about 56.52 m.