Circumference and Area of Circles & Semi-Circles

Front

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

Back

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

Front

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

Back

Area = π × radius².

Front

What is the diameter of a circle?

Back

The diameter is the distance across the circle through the center.

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

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

Back

Diameter = 2 × radius = 2 × 7 cm = 14 cm.

Front

If the diameter of a circle is 10 cm, what is the circumference?

Back

Circumference = π × diameter = π × 10 cm ≈ 31.42 cm.

Front

True or False: The radius is half the diameter.

Back

True.

Front

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

Back

Circumference = 2 × π × 5 cm ≈ 31.42 cm.

Front

What is the area of a circle with a radius of 3 cm?

Back

Area = π × (3 cm)² ≈ 28.27 cm².

Front

What is the circumference of a semi-circle with a diameter of 8 cm?

Back

Circumference of semi-circle = (π × diameter / 2) + diameter = (π × 8 cm / 2) + 8 cm ≈ 20.57 cm.