Question

The radius of a circle is 20 cm. Three more concentric circles are drawn inside it in such a manner that it is divided into four parts of equal area. Find the radius of the largest of the three concentric circle in cm.

Answer 1

The area of the given circle = $\pi (20{)}^2$ = 400$\pi c{m}^2$

If it is divided in 4 equal parts according to area, the smallest circle should have the area of 100$\pi$.

The circle with largest area will be circle with area of 300$\pi c{m}^2$

Its radius will be = $\sqrt{\frac{300\pi }{\pi }}$ = 17.32 cm.