Circumference & Area of Circles Practice

Answer 1

1. Find the circumference of a circle with a radius of 5 cm.

Circumference = 2 * π * radius
Circumference = 2 * 3.14 * 5
Circumference = 31.4 cm

2. Find the area of a circle with a diameter of 12 inches.

Radius = diameter / 2
Radius = 12 / 2
Radius = 6 inches

Area = π * radius^2
Area = 3.14 * 6^2
Area = 3.14 * 36
Area = 113.04 square inches

3. Find the circumference of a circle with an area of 50 square meters.

Radius = √(area / π)
Radius = √(50 / 3.14)
Radius = √15.92
Radius ≈ 3.99 meters

Circumference = 2 * π * radius
Circumference = 2 * 3.14 * 3.99
Circumference ≈ 25.05 meters

4. Find the area of a circle with a circumference of 30 cm.

Radius = circumference / (2 * π)
Radius = 30 / (2 * 3.14)
Radius ≈ 4.77 cm

Area = π * radius^2
Area = 3.14 * 4.77^2
Area ≈ 71.27 cm²

5. Find the circumference of a circle with an area of 100 square inches.

Radius = √(area / π)
Radius = √(100 / 3.14)
Radius = √31.85
Radius ≈ 5.65 inches

Circumference = 2 * π * radius
Circumference = 2 * 3.14 * 5.65
Circumference ≈ 35.48 inches