Question

Find the circumference of the circle with the following radius (Take \[\;\pi = \dfrac{{22}}{7}\])
(a) $14cm$
(b) $28cm$
(c) $21cm$

Answer 1

Hint: In Mathematics, the circumference is the boundary that surrounds the shape. That is, the circumference of the circle is the measure of the boundary of the circle and it is the same as the perimeter. Generally, we use the word circumference instead of the perimeter in the circle. The word perimeter is commonly used for square, rectangle, and triangle.
Here, we are given three radii to calculate the circumference of the circle for each radius.

Formula used:
The formula to calculate the circumference of the circle when the radius is given is as follows.
The circumference of the circle, \[C = 2\pi r\]
Where $r$ is the radius of the circle.
Complete step by step answer:

We need to calculate the circumference of the circle for each radius.
(a) The given radius of the circle is $14cm$.
Now, we need to apply the formula.
The circumference of the circle, \[C = 2\pi r\]
 $ = 2\pi \times 14$
$ = 2 \times \dfrac{{22}}{7} \times 14$
$ = 2 \times 22 \times 2$
$ = 88cm$
Hence, the circumference of the circle for the radius $14cm$ is $88cm$
(b) The given radius of the circle is $28cm$.
Now, we need to apply the formula.
The circumference of the circle,\[C = 2\pi r\]
\[ = 2\pi \times 28\]
$ = 2 \times \dfrac{{22}}{7} \times 28$
$ = 2 \times 22 \times 4$
$ = 176cm$
Hence, the circumference of the circle for the radius $28cm$ is $176cm$
(c) The given radius of the circle is $21cm$.
Now, we need to apply the formula.
The circumference of the circle, \[C = 2\pi r\]
$ = 2\pi \times 21$
$ = 2 \times \dfrac{{22}}{7} \times 21$
$ = 2 \times 22 \times 3$
$ = 132cm$
Hence, the circumference of the circle for the radius $21cm$ is $132cm$

Note: Generally, the circumference denotes the path that surrounds the shape.
The formula to calculate the circumference of the circle when the diameter is given is as follows.
The circumference of the circle, \[C = \pi D\] (We know that diameter$ = 2 \times radius$)
Where $D$ is the Diameter of the circle.