Question

Find the circumference of the inner and the outer circles, shown in the adjoining figure?(Take $\pi =3.14$)

Answer 1

Step 1. Find the circumference of the outer circle.

From the above figure it is clear that the radius of the outer circle is $19m$

Let Radius $=r$ and Circumference $=C$

$Circumferenceofcircle\left(C\right)=2\pi r$

$r=19$

$$\begin{gathered} C=2\pi r \\ \Rightarrow C=2\times (3.14)\times 19 \\ =119.32 \end{gathered}$$

So, the circumference of the outer circle is $119.32m$

Step 2. Find the circumference of the inner circle.

From the above figure it is clear that the radius of the inner circle is $(19-10)=9m$

Let Radius $=r$ and Circumference $=C$

$Circumferenceofcircle\left(C\right)=2\pi r$

$r=9$

$$\begin{gathered} C=2\pi r \\ \Rightarrow C=2\times (3.14)\times 9 \\ =56.52 \end{gathered}$$

So, the circumference of the inner circle is $56.52m$

Hence, the circumference of the outer circle is $119.32m$ and the circumference of the inner circle is $56.52m$.