Question

The radius of a circle is $5m$. Find the circumference of the circle whose area is $49$ times the area of the given circle.

• A. $220m$
• B. $120m$
• C. $320m$
• D. $420m$

Answer 1

The correct option is A $220m$

Radius of given circle $=5cm$

Therefore,

Area of given circle $=\pi (5{)}^2$

$=25\pi c{m}^2$

Let radius of required circle $=r$

Therefore,

$\pi r^2=49\times 25\pi$

$\Rightarrow r^2=(7\times 5{)}^2$

$\Rightarrow r=35$

Therefore,

Circumference $=2\pi r$

$=2\times \frac{22}{7}\times 35$

$=220m$