In $Fig.$ a circle is inscribed in a square of side $5 \,cm$ and another circle is circumscribing the square. Is it true to say that area of the outer circle is two times the area of the inner circle? Give reasons for your answer.
It is true, because diameter of the inner circle $=5 \,cm$ and that of outer circle $=$ diagonal of the square $=5 \sqrt{2} \,cm$
$So , A _{1}=\pi\left(\frac{5 \sqrt{2}}{2}\right)^{2}$ and $A _{2}=\pi\left(\frac{5}{2}\right)^{2},$ giving $\frac{ A _{1}}{ A _{2}}=2$
In a circle, the area of a sector formed by two radii perpendicular to each other is $38.5 \,cm ^{2}$. Find the radius of the circle. (in $cm$)
Find the area of the shaded region in $Fig.$ where arcs drawn with centres $A , B , C$ and $D$ intersect in pairs at mid-points $P , Q , R$ and $S$ of the sides $AB , BC,$ $CD$ and $DA ,$ respectively of a square $ABCD$ (Use $\pi=3.14)$ (in $cm ^{2}$)
In a circle with radius $7\,cm ,$ the area of a minor sector can be $\ldots \ldots \ldots \ldots cm ^{2}$.
The perimeter of a semicircular table-top is $3.60\,m .$ Then, its radius is $\ldots \ldots \ldots . . cm .$
Area of the largest triangle that can be inscribed in a semi-circle of radius $r$ units is