The union of a chord of a circle and its corresponding arc is called $\ldots \ldots \ldots \ldots$

Find the diameter of the circle whose area is equal to the sum of the areas of the two circles of diameters $20 \, cm$ and $48 \, cm$. (in $cm$)

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

$A$ 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 $cm$)

The length of a square field is $50 \, m$. $A$ cow is tethered at one of the vertices by a $3 \, m$ long rope. Find the area of the region of the field in which the cow can graze. $(\pi = 3.14)$ (in $m^2$)

The ratio of the areas of the circles with radii $8 \, cm$ and $12 \, cm$ is $\ldots \ldots \ldots \ldots .$