Circle Measurements and Calculations

Circle Measurements and Definitions

• Circumference is the distance around a circle.
• Diameter is the distance across a circle through its center.
• Radius is the distance from the center of a circle to any point on the circle.

Relationship Between Diameter and Radius

• Diameter is twice the radius (d = 2r).
• For a radius of 2 inches, the diameter is 4 inches.
• For a radius of 15.3 centimeters, the diameter is 30.6 centimeters.

Calculating Circumference

• Circumference can be calculated using the formula: C = πd or C = 2πr.
• For a diameter of 3 centimeters, the circumference is approximately 9.42 cm.
• For a radius of 2 inches, the circumference is approximately 12.56 inches.
• For a circle with a diameter of 7.5 inches, the circumference is approximately 23.55 inches.

Calculating Area

• Area of a circle is calculated using the formula: A = πr².
• An 8-centimeter diameter circle has an area of approximately 50.24 cm².
• A circle with a radius of 3 inches has an area of approximately 28.26 in².
• For a radius of 9 centimeters, the area is approximately 254.34 cm².
• A circular rug with a radius of 4 feet has an area of approximately 50.24 feet².
• A bicycle wheel with a diameter of 20 inches has an area of approximately 314 in².

Specific Area Calculations

• For a diameter of 10 centimeters, the area is approximately 78.5 cm².
• The area calculations demonstrate that the area increases with both radius and diameter measurements.

Additional Geometry Terms

• A line segment is a part of a line bounded by two endpoints.
• A chord is a line that links two points on the circumference of the circle.