7.9B Circumference and Area of Circles

Front

What is the formula for calculating the circumference of a circle?

Back

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

Front

If a circle has a diameter of 10 feet, what is its circumference?

Back

Circumference = π × 10 ft ≈ 31.42 ft.

Front

What does 'area' mean in relation to a circle?

Back

Area is the space a circle takes up, calculated as Area = π × radius².

Front

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

Back

Radius = diameter ÷ 2.

Front

What is the diameter of a circle with a radius of 5 cm?

Back

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

Front

What is the approximate value of π (pi)?

Back

π ≈ 3.14.

Front

A circle has a radius of 3 inches. What is its area?

Back

Area = π × (3 in)² ≈ 28.26 in².

Front

What is the circumference of a circle with a radius of 4 meters?

Back

Circumference = 2 × π × 4 m ≈ 25.13 m.

Front

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

Back

Diameter = Circumference ÷ π ≈ 31.4 cm ÷ 3.14 ≈ 10 cm.

Front

What is the relationship between diameter and circumference?

Back

The circumference is always π times the diameter.