Find the area of a sector of a circle of radius $28 \,cm$ and central angle $45^{\circ}$. (in $cm^{2}$)

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 areas of two sectors of two different circles are equal. Is it necessary that their corresponding arc lengths are equal? Why?

In $\odot(O, r)$,minor arc $\widehat{ABC}$ subtends a right angle at the centre. The area of the minor segment formed by $\widehat{ABC}$ is $14.25\,cm^2$ and the area of $\Delta OAC$ is $25\,cm^2$. Then,the area of the minor sector formed by $\widehat{ABC}$ is $\ldots \ldots \ldots cm^2$.

The ratio of the radii of two circles is $4: 5$. Then,the ratio of their areas is...........

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 $\text{cm}^2$)