$A$ piece of wire $20 \,cm$ long is bent into the form of an arc of a circle subtending an angle of $60^{\circ}$ at its centre. Find the radius of the circle. (in $cm$)

The perimeter of a semicircular table-top is $3.60 \, m$. Then,its radius is $\ldots \ldots \ldots \, cm$.

In the adjoining figure,$PS$ is the diameter of a circle and $PS = 12$. $PQ = QR = RS$. Semicircles are drawn with diameters $\overline{PQ}$ and $\overline{QS}$. Find the perimeter and the area of the shaded region. $(\pi = 3.14)$

The side length of square $ABCD$ is $14 \, cm$. As shown in the diagram,circles with radius $7 \, cm$ are drawn with each vertex as the centre so that each circle touches two other circles externally. Find the area of the shaded region in $cm^2$.

As shown in the diagram,$\overline{OA}$ and $\overline{OB}$ are two radii of $\odot(O, 35 \text{ cm})$ perpendicular to each other. If $OD = 12 \text{ cm}$,find the area of the shaded region. (in $\text{cm}^2$)

In $\odot(O, 12)$, minor $\widehat{ACB}$ subtends an angle of measure $30^{\circ}$ at the centre. Then, the length of major $\widehat{ADB}$ is $\ldots \ldots \ldots \text{ cm}$. (in $\pi$)