The area of a circle is $200 \, cm^{2}$. Then,the area of a minor sector of that circle can be $\ldots \ldots \ldots \, cm^{2}$.

As shown in the diagram,the radii of two concentric circles are $21 \, cm$ and $28 \, cm$. If $m \angle AOB = 40^\circ$,find the area of the shaded region. (in $cm^2$)

The circumference of a circle with radius $8.4\,cm$ is $\ldots \ldots \ldots \ldots cm$.

The area of the circle that can be inscribed in a square of side $6 \, cm$ is (in $cm^2$) (in $\pi$)

An archery target has three regions formed by three concentric circles as shown in the figure. If the diameters of the concentric circles are in the ratio $1: 2: 3$,then find the ratio of the areas of the three regions.

In covering a distance $s$ metres,a circular wheel of radius $r$ metres makes $\frac{s}{2 \pi r}$ revolutions. Is this statement true? Why?