The slant height and base diameter of a conical tomb are $25 \, m$ and $14 \, m$ respectively. Find the cost of white-washing its curved surface at the rate of $Rs. 210$ per $100 \, m^2$.

$A$ metal pipe is $77 \, cm$ long. The inner diameter of a cross section is $4 \, cm$ and the outer diameter is $4.4 \, cm$ (see Fig.). Find its total surface area. (in $, cm^2$)

The front compound wall of a house is decorated by wooden spheres of diameter $21 \, cm,$ placed on small supports as shown in the figure. Eight such spheres are used for this purpose,and are to be painted silver. Each support is a cylinder of radius $1.5 \, cm$ and height $7 \, cm$ and is to be painted black. Find the cost of paint required if silver paint costs $25$ paise per $cm^2$ and black paint costs $5$ paise per $cm^2$.

$A$ right triangle $ABC$ with sides $5 \, cm, 12 \, cm$ and $13 \, cm$ is revolved about the side $12 \, cm$. Find the volume of the solid so obtained. Also,find the volume of the solid obtained when the same triangle is revolved about the side $5 \, cm$. Finally,find the ratio of the volumes of the two solids.

Find the amount of water displaced by a solid spherical ball of diameter $28 \, cm$.

Find the surface area of a sphere of radius $14 \, cm$.
Assume $\pi = \frac{22}{7}$. (in $, cm^2$)