Circles

Front

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

Back

Circumference = π × d (where d is the diameter) or Circumference = 2 × π × r (where r is the radius).

Front

If a circle has a diameter of 8 cm, what is its radius?

Back

Radius = 4 cm (since radius is half of the diameter).

Front

What is the relationship between the radius and diameter of a circle?

Back

The radius is half of the diameter: r = (1/2)d.

Front

What is the circumference of a circle with a radius of 1 inch?

Back

6.28 in (Circumference = 2 × π × 1 in).

Front

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

Back

31.4 m (Circumference = π × 10 m).

Front

What do we call the distance around a circle?

Back

Circumference.

Front

If the circumference of a circle is 25.12 cm, what is its diameter?

Back

Diameter = 8 cm (using the formula d = C/π).

Front

What is the value of π (pi) approximately?

Back

π ≈ 3.14.

Front

How do you find the area of a circle?

Back

Area = π × r².

Front

If a circle has a radius of 3 cm, what is its area?

Back

Area = 28.26 cm² (Area = π × 3²).