The area of a sector formed by a $12\,cm$ long arc in a circle with radius $12\,cm$ is $\ldots \ldots \ldots \, cm^{2}$.

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

The circumference of a circle is $176\,cm$. Then,its radius is $\ldots \ldots \ldots \ldots cm$.

In a circle with radius $8.4 \, cm$,two radii are perpendicular to each other. The area of the minor sector formed by these radii is $\ldots \ldots \ldots \, cm^2$.

$A$ 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 $cm$)

In a circle,the ratio of the areas of two distinct minor sectors is $1:4$. Then,the ratio of the angles at the centre for those minor sectors is $\ldots \ldots \ldots \ldots$.