Area and Circumference of Circles

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 twice the length of the radius and is the distance across the circle through its center.

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 a circle has a radius of 6 inches, what is its diameter?

Back

Diameter = 2 × radius = 2 × 6 = 12 inches.

Front

If a circle has a diameter of 20 inches, what is its radius?

Back

Radius = diameter ÷ 2 = 20 ÷ 2 = 10 inches.

Front

What is the circumference of a circle with a radius of 10 inches?

Back

Circumference = 2 × π × 10 ≈ 62.83 inches.

Front

What is the area of a circle with a radius of 10 inches?

Back

Area = π × 10² ≈ 314.16 square inches.

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 inches, what is its radius?

Back

Radius = Circumference ÷ (2 × π) ≈ 5 inches.