Question

Find the diameter of the circle whose circumference is $42cm$.

Answer 1

Given: The circumference of the circle is $42$ cm.

Let the radius and diameter of the circle are $r$ and $d$, respectively.

We know that,

Circumference $=2\pi r$

$\therefore 2\pi r=42$

$\Rightarrow 2\left(\frac{22}{7}\right)r=42$

$\Rightarrow r=\frac{147}{22}\approx 6.68$ cm

Since, the diameter of the circle is twice of it radius.

$\therefore d=2r$

$\Rightarrow d=2\left(\frac{147}{22}\right)=\frac{147}{11}\approx 13.36$

Thus, the diameter of the given circle is $\frac{147}{11}$ cm or $13.36$ (approx) cm.