As you know, a circle is a shape with all points the same distance from the center. When the distance around a circle is measured and divided by the distance across the same circle through the center, you will always come close to the value aproximately 3.14159265358979323846... The unit used to represent this value is π. Even up till now, mathematicians are calculating the exact number of π as the value goes on forever. 
The distance around a circle is called the circumference of the circle, while the distance across a circle is called the diameter. To find the circumference of a circle, you have to take the diameter and multiply it by the value of π which is commonly simplified to 3.142. This is possible as for any circle, if you divide the circumference by the diameter, you can get the value of 3.142 rounded to 3 decimal places. Thus the formula of finding the circumference of a circle is d x π = c 
The radius of a circle is the distance for the center of the circle to any point on the circumference. Therefore, two radi (plural for radius) of a circle placed end to end of each other will form the diameter of a circle. Thus producing the formula,d = 2r , where d is the diameter and r is the radius.
A real-life application using the circumference of a circle is the measuring of the circumference of your dinning plate. To find the circumference of circular objects in real-life like your dinning plate, you can use a measuring instrument to find the diameter of the plate and apply the d x π = c formula. For example if your plate is 9 inches in diameter, taking 9 x π , you can find out that your plate is actually around 28.3 inches in diameter.
Done by Danny Ng
