Radius, Diameter, and Circumference

Front

What is the formula to calculate the circumference of a circle?

Back

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

Front

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

Back

Diameter = 2 × radius = 14 cm.

Front

What is the radius of a circle with a diameter of 20 inches?

Back

Radius = Diameter ÷ 2 = 10 inches.

Front

How do you find the circumference of a circle with a radius of 10 mm?

Back

Circumference = 2 × π × 10 mm ≈ 62.83 mm.

Front

What does the term 'diameter' refer to in 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 circumference of 31.4 cm, what is its radius?

Back

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

Front

What is the relationship between radius and diameter?

Back

The diameter is always twice the length of the radius.

Front

If the diameter of a circle is 30 feet, what is the circumference?

Back

Circumference = π × diameter = π × 30 feet ≈ 94.25 feet.

Front

What is the radius of a circle with a circumference of 62.83 cm?

Back

Radius = Circumference ÷ (2 × π) ≈ 10 cm.

Front

What is the circumference of a circle with a radius of 15 cm?

Back

Circumference = 2 × π × 15 cm ≈ 94.25 cm.