Circumference and Area of a Circle

Front

What is the formula for the area of a circle?

Back

Area = π × r², where r is the radius.

Front

What is the formula for the circumference of a circle?

Back

Circumference = 2 × π × r or Circumference = π × d, where r is the radius and d is the diameter.

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 10 m, what is the circumference?

Back

31.4 m (Circumference = π × 10 ≈ 31.4).

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

If the radius of a circle is doubled, how does the area change?

Back

The area increases by a factor of 4.

Front

What is the approximate value of π?

Back

π ≈ 3.14.

Front

If a circle has a circumference of 62.8 m, what is its diameter?

Back

20 m (Diameter = Circumference / π ≈ 20).

Front

What is the area of a circle with a radius of 5 ft?

Back

78.5 ft² (Area = π × 5² ≈ 78.5).

Front

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

Back

Radius = √(Area / π).