The area of a circle is $220 \mathrm{~cm}^{2}$. The area of ta square inscribed in it is
(a) $49 \mathrm{~cm}^{2}$
(b) $70 \mathrm{~cm}^{2}$
(c) $140 \mathrm{~cm}^{2}$
(d) $150 \mathrm{~cm}^{2}$
Let BD be the diameter and diagonal of the circle and the square respectively.
We know that area of the circle $=\pi r^{2}$
Area of the circle $=\pi r^{2}$
$\therefore 220=\frac{22}{7} \times r^{2}$
Multiplying both sides of the equation by 7 we get,
$220 \times 7=22 \times r^{2}$
Dividing both sides of the equation by 22 we get,
$\therefore r^{2}=70$
$\therefore r=\sqrt{70}$
As we know that diagonal of the square is the diameter of the square.
$\therefore$ Diagonal $=2 r$
$\therefore$ Diagonal $=2 \sqrt{70}$
$\therefore$ Side of the square $=\frac{\text { diagonal }}{\sqrt{2}}$.......(1)
Substituting Diagonal $=2 \sqrt{70}$ in equation (1) we get,
Side of the square $=\frac{2 \sqrt{70}}{\sqrt{2}}$
$\therefore$ Side of the square $=2 \sqrt{\frac{70}{2}}$
$\therefore$ Side of the square $=2 \sqrt{35}$
$\therefore$ Area of the square $=\operatorname{side}^{2}$
$=(2 \sqrt{35})^{2}$
$=4 \times 35$
$=140$
Therefore, area of the square is $140 \mathrm{~cm}^{2}$
Hence, the correct answer is option (c).