Measuring Circumferences

This video lesson is designed for 6-12-year-old children to help them understand what is the circumference of a circle and how it is calculated.

In our previous video lesson, we learned about various parts of a circle. In this video, we will learn about the circumference of the circle.

What is the Circumference of a Circle?

The circumference of a circle is the distance around the circle. It is the perimeter of a circle. Every point on the circumference of a circle is equidistant from the center of the circle. This means that if you draw a line from the center of the circle to any point on the circumference, it will be the same length as any other line drawn from the center to a different point on the circumference.

How to Calculate the Circumference of a Circle?

The formula for calculating the circumference of a circle is

2πr or πd, where r is the radius of the circle and d is the diameter of the circle.

The value of π is a mathematical constant that is approximately equal to 3.14159. It is an irrational number, which means that its decimal representation goes on forever without repeating.

Therefore, the circumference of a circle can be calculated by multiplying the diameter of the circle by π (pi) or by multiplying the radius of the circle by 2 and then multiplying that value by π. This means that if you know either the diameter or the radius of a circle, you can easily calculate its circumference using one of these formulas.

For example, if the radius of a circle is 5 cm, then the circumference of the circle will be 2 x 5 x π = 10π cm. Similarly, if the diameter of a circle is 10 cm, then the circumference of the circle will be π x 10 = 10π cm.

Usage of the Circumference of a Circle in Daily Life

The circumference of a circle is an important parameter that helps in understanding the geometric properties of a circle, and it has numerous applications in our daily lives.

• It helps understand the geometric properties of a circle and has numerous applications in daily life.
• It is used in determining the distance traveled by a car’s wheels, calculating the length of a pipe or cable required for a specific job, or the amount of fencing needed to enclose a circular area.
• It is used in construction to calculate the amount of material needed to build a circular structure, such as a silo or a water tank.
• It is an important geometric property used in mathematics, engineering, and physics. It is the distance around the circle. In mathematics, it is used to calculate the area of the circle with the formula πr^2. In engineering, it is used to design circular objects like gears, wheels, and pulleys. In physics, it is used to calculate the distance traveled by an object in a circular path.
• It is used in landscaping to calculate the amount of mulch or gravel needed to cover a circular flower bed or a circular patio.
• It is crucial for determining the size and weight of the ball in sports, which is important for the performance of the players.
• It is used in navigation, astronomy, and many other fields.

Repeat this activity by asking the child to measure the circumference of the different circular objects in the house as shown in the video.

Related Video Resources

• Understanding Geometry
• Area of Rectangle
• Area of Triangle

To watch more math video resources, click here. 

Video Created by: Justine McNeilly

FAQs

• Why is the circumference of a circle 2πr?

The circumference of a circle is 2πr because π (pi) is the ratio of the circle’s circumference to its diameter, and the diameter is twice the radius (d=2r). Therefore, the formula for the circumference of a circle is C=πd=2πr.

• What is π circumference of a circle?

The value of π (pi) is a mathematical constant that represents the ratio of the circumference of a circle to its diameter. Therefore, to find the circumference of a circle, you multiply its diameter by π.

• How is the circumference of a circle calculated?

The circumference of a circle is calculated using the formula C = 2πr, where C is the circumference, π is the mathematical constant pi (approximately equal to 3.14159), and r is the radius of the circle.