Surface area of a sphere $= \dots \dots \dots \dots .$

How many cones with diameter $7\,cm$ and height $3\,cm$ can be produced by melting a metallic sphere with diameter $21\,cm$?

The diameters of the two circular ends of the bucket are $44 \, cm$ and $24 \, cm$. The height of the bucket is $35 \, cm$. The capacity of the bucket is (in $L$): (in $.7$)

The radii of a frustum of a cone are $28 \, cm$ and $7 \, cm$ and its height is $72 \, cm$. Find its curved surface area,total surface area,and volume.

The shape of a glass (tumbler) (see figure) is usually in the form of:

Write 'True' or 'False' and justify your answer:
The volume of the frustum of a cone is $\frac{1}{3} \pi h[r_{1}^{2} + r_{2}^{2}-r_{1} r_{2}],$ where $h$ is the vertical height of the frustum and $r_{1}, r_{2}$ are the radii of the ends.