The area of a circle is 49 π cm2. Its circumference is

Question:

The area of a circle is 49 π cm2. Its circumference is
(a) 7 π cm
(b) 14 π cm
(c) 21 π cm
(d) 28 π cm

Solution:

(b) 14π cm
Let the radius be r cm.
We know:

Area of a circle $=\pi r^{2}$

Thus, we have:

$\pi r^{2}=49 \pi$

$\Rightarrow r^{2}=49$

$\Rightarrow r=\sqrt{49}$

$\Rightarrow r=7$

Now,

Circumference of the circle $=2 \pi \mathrm{r}$

$=\left(2 \times \frac{22}{7} \times 7\right) \mathrm{cm}$

$=14 \pi \mathrm{cm}$

 

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