Area and Circumference of Circles

Front

What is the definition of a radius in a circle?

Back

A radius is a line segment from the center of the circle to any point on its circumference.

Front

What is the definition of a diameter in a circle?

Back

A diameter is a line segment that passes through the center of the circle and has its endpoints on the circumference. It is twice the length of the radius.

Front

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

Back

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

Front

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

Back

Area = π × radius².

Front

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

Back

154 cm² (Area = π × 7² = 154).

Front

If the diameter of a circle is 20 cm, what is the radius?

Back

10 cm (Radius = diameter ÷ 2).

Front

What is the circumference of a circle with a radius of 5 m?

Back

31.4 m (Circumference = 2 × π × 5).

Front

What is the area of a circle with a diameter of 10 m?

Back

78.5 m² (Area = π × (5)² = 78.5).

Front

What is the relationship between diameter and radius?

Back

The diameter is twice the length of the radius.

Front

What is the circumference of a circle with a diameter of 12 cm?

Back

37.7 cm (Circumference = π × 12).