In $\odot(O, 4 \, cm)$,the length of chord $\overline{AB}$ is $4 \, cm$. Then,$m \angle AOB = \ldots$ (in $^\circ$)

Is it true that the distance travelled by a circular wheel of diameter $d \text{ cm}$ in one revolution is $2 \pi d \text{ cm}$? Why?

The diameter of a circle with area $154\,cm^{2}$ is $\ldots \ldots \ldots . cm$.

Nine circular designs are made in a square show-piece as shown in the diagram. If the radius of each circle is $21\, cm$,find the area of the region without design. (in $cm^2$)

Find the difference of the areas of two segments of a circle formed by a chord of length $5 \, cm$ subtending an angle of $90^{\circ}$ at the centre.

Find the area of the segment of a circle of radius $12 \, cm$ whose corresponding sector has a central angle of $60^{\circ}$ (Use $\pi = 3.14$).