A cylinder of same height and radius is placed on the top of a hemisphere. Find the curved surface area of the shape if the length of the shape be $7 \mathrm{cm}$. 

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

Find the volume of a sphere whose radius is $2 \mathrm{cm}$( in ${\mathrm{cm}}^3$)

Find the volume of a sphere whose radius is:

$3.5 \mathrm{cm}$

Find the volume of a sphere whose radius is $10.5 \mathrm{cm}$ (${\mathrm{cm}}^3$).