Find the diameter of a circle whose circumference is 66m.

- Hint: In this question we are asked to find the diameter with the given circumference. To find this first we need to find the radius of a circle by taking the formula of circumference of a circle $=2\pi r$. Then find diameter where $d=2r$.

Complete step-by-step solution -

To find the diameter of a circle, let us first find the radius of a circle.
It is given that circumference of a circle = 66m.
We know that circumference of a circle $=2\pi r$ . So, equating it to 66 m, we get
$66=2\times \dfrac{22}{7}\times r$
Divide ‘2’ on both sides, we get –
$33=\dfrac{22}{7}\times r$
Multiply both sides by ‘7’ we get –
$231=22r$
Divide both sides by ‘22’ we get –
$\dfrac{231}{22}=r$
$r=10.5$
Now, let us find the diameter, where \[d=2r\] .
Here, we will put the value of $r=10.5$
$\begin{align}
  & d=2\times 10.5 \\
 & d=21 \\
\end{align}$
Hence, the diameter of the circle is 21 m.

Note: Circumference of Circle: The distance around the circular region is called its circumference. The ratio of circumference of any circle to its diameter is constant. This constant is denoted by $\pi $ and is read as pie. $\dfrac{\text{circumference}}{diameter}=\pi $ or Circumference of a circle $=2\pi r$ , where ‘r’ denoted as the radius of the circle. So, using this relation also, we can directly get the diameter.