$A$ dome of a building is in the form of a hemisphere. From inside,it was white-washed at the cost of $Rs. 4989.60$. If the cost of white-washing is $Rs. 20$ per square metre,find the volume of the air inside the dome. (in $, m^3$)

$A$ conical tent is $10 \, m$ high and the radius of its base is $24 \, m$. Find the cost of the canvas required to make the tent,if the cost of $1 \, m^2$ canvas is $Rs. 70$.

Find how much steel was actually used to make a closed cylindrical tank (radius $2.1 \text{ m}$, height $4.5 \text{ m}$), if $1/12$ of the steel actually used was wasted in making the tank. [Assume $\pi = 22/7$] (in $\text{ m}^2$)

$A$ lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in the interior. The diameter of the pencil is $7 \,mm$ and the diameter of the graphite is $1 \,mm$. If the length of the pencil is $14 \,cm$,find the volume of the wood and that of the graphite. (in $,cm^3$)

Find the volume of a sphere whose radius is $7 \, cm$. Assume $\pi = \frac{22}{7}$.

Find the amount of water displaced by a solid spherical ball of diameter $0.21 \, m$. (in $, m^3$)