Area and Circumference 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 d is the diameter.

Front

If a circle has a radius of 7 inches, what is its area?

Back

154 square inches (Area = π × 7² ≈ 154).

Front

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

Back

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

Front

What is the relationship between diameter and radius?

Back

Diameter = 2 × Radius.

Front

How do you convert diameter to radius?

Back

Radius = Diameter ÷ 2.

Front

What is the approximate value of π?

Back

π ≈ 3.14.

Front

If a circular rug has a radius of 4 feet, what is its area?

Back

50.3 square feet (Area = π × 4² ≈ 50.3).

Front

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

Back

31.4 inches (Circumference = 2 × π × 5 ≈ 31.4).

Front

If the circumference of a circle is 20 inches, what is the radius?

Back

Approximately 3.2 inches (Radius = Circumference ÷ (2 × π) ≈ 3.2).