Question

The radius of a circle is 20 cm Three more concentric circles are drawn inside it in such a way that it is divided into four parts of equal area then radius of one of the three concentric circles is

• A. $2\sqrt{2}$ cm
• B. $8\sqrt{3}$ cm
• C. $10\sqrt{3}$ cm
• D. $14\sqrt{3}$ cm

Answer 1

The correct option is C $10\sqrt{3}$ cm

Let r cm can be the radius of the three concentric circles

Then the area of concentric circles=$\pi r^2$

But it is divided into four part of equal area then the radius of one of the three circles

Then $\pi r^2=\frac{3}{4}\pi (20{)}^2\Rightarrow r^{2}300\Rightarrow r=10\sqrt{3}$cm