Circles: Circumference and Area

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

How do you calculate the circumference of a circle?

Back

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

Front

What is the formula for the area of a circle?

Back

Area = π × radius².

Front

If the radius of a circle is 9, what is the diameter?

Back

Diameter = 2 × radius = 2 × 9 = 18.

Front

If the diameter of a circle is 7, what is the radius?

Back

Radius = diameter ÷ 2 = 7 ÷ 2 = 3.5.

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

What is the circumference of a circle with a radius of 6?

Back

Circumference = 2 × π × 6 ≈ 37.68.

Front

What is the area of a circle with a radius of 6?

Back

Area = π × 6² ≈ 113.04.

Front

If a circle has an area of 1134.11, what is its radius?

Back

Radius = √(Area/π) ≈ √(1134.11/3.14) ≈ 19.