How to calculate Circumference of a circle using the radius?

According to the formula for the calculations of the circumference, it requires only radius(r).

Example-1 :

The radius of a circle is 7.5 inches. What is the circumference?

$$\text{C}\;=\;2πr$$

$$\text{C}\;=\;2(3.14)(7.5)$$

$$\text{C}\;=\;47.1\;\text{inches}$$

How to calculate Circumference of a circle using the diameter?

According to the formula for the calculations of the circumference, it requires only diameter(r).

Example-2:

The diameter of a circle is 5 centimetres. What is the circumference?

$$\text{C}\;=\;π\;*\;\text{d}$$

$$\text{C}\;=\;π\;*\;5$$

$$\text{C}\;=\;3.14\;*\;5$$

$$\text{C}\;=\;15.7\;\text{cm}$$