The radius of a circle is $12 \, cm$. Find its circumference and area $(\pi = 3.14)$.

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 formula to find the length of a major arc of a circle is ............

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 $\pi$)

Will it be true to say that the perimeter of a square circumscribing a circle of radius $a \, cm$ is $8 a \, cm$? Give reasons for your answer.

In the figure,$ABCD$ is a trapezium with $AB \parallel DC$,$AB = 18 \, cm$,$DC = 32 \, cm$,and the distance between $AB$ and $DC = 14 \, cm$. If arcs of equal radii $7 \, cm$ with centers $A, B, C$,and $D$ have been drawn,find the area of the shaded region of the figure (in $cm^2$).