Let's solve the following problems to understand it further:
1. Find the circumference of a circle whose diameter is 6 inches. (pi = 3.14)
Solution: Given diameter of the circle = d = 6 in.
Formula >>>> C = pi x diameter of the circle
C = 3.14 x 6 = 18.84 inches
Note: Remember that the units of circumference is same as that of the diameter of radius of the circle. Many students confuse with the units of area and circumference. Don't square the units for circumference (perimeter) of a circle because it represent a length not the area.
2. A circle has a radius of 2.5 cm, find its circumference. Use pi = 3.14
Solution: Given the radius of the circle = r = 2.5 cm
Formula to find the circumference of a circle when its radius is given, shown below:
C = 2 x pi x radius (r)
C = 2 x 3.14 x 2.5
C = 15.7 cm
Worksheets on the above concept: Print the following worksheets to practice how to find the circumference of a circle when its diameter of radius is given.
Worksheet  1 Worksheet  2 Word Problems Worksheet
