Find the lateral or curved surface area of a closed cylindrical petrol storage tank that is $4.2\, m$ in diameter and $4.5\, m$ high. $\left[\text{Assume } \pi = \frac{22}{7}\right]$ (in $, m^2$)

$A$ wooden bookshelf has external dimensions as follows: Height $= 110\, cm$,Depth $= 25\, cm$,Breadth $= 85\, cm$ (see Fig.). The thickness of the plank is $5\, cm$ everywhere. The external faces are to be polished and the inner faces are to be painted. If the rate of polishing is $20$ paise per $cm^2$ and the rate of painting is $10$ paise per $cm^2$,find the total expenses required for polishing and painting the surface of the bookshelf.

The inner diameter of a circular well is $3.5\, m$. It is $10\, m$ deep. Find the cost of plastering this curved surface at the rate of $Rs. 40$ per $m^2$.

The capacity of a cuboidal tank is $50000$ litres of water. Find the breadth of the tank,if its length and depth are respectively $2.5\, m$ and $10\, m$. (in $, m$)

Find the volume of the right circular cone with radius $6 \, cm$ and height $7 \, cm$. Assume $\pi = \frac{22}{7}$. (in $, cm^3$)

$A$ corn cob (see figure),shaped somewhat like a cone,has the radius of its broadest end as $2.1\, cm$ and length (height) as $20\, cm$. If each $1\, cm^2$ of the surface of the cob carries an average of four grains,find how many grains you would find on the entire cob.