$A$ school provides milk to the students daily in cylindrical glasses of diameter $7\, cm$. If the glass is filled with milk up to a height of $12\, cm$, find how many litres of milk is needed to serve $1600$ students. (in $0.2$)

The radii of five metal spheres are $1\, cm, 3\, cm, 4\, cm, 5\, cm$ and $8\, cm$ respectively. If they are melted and cast into a single large sphere,find the radius of that sphere. Furthermore,if this large sphere is melted and recast into smaller cylinders,each with a radius of $3\, cm$ and a height of $4\, cm$,how many such cylinders can be formed?

The paint in a certain container is sufficient to paint an area equal to $9.375 \,m^2$. How many bricks of dimensions $22.5 \,cm \times 10 \,cm \times 7.5 \,cm$ can be painted out of this container?

$A$ plastic box $1.5\, m$ long,$1.25\, m$ wide,and $65\, cm$ deep is to be made. It is opened at the top. Ignoring the thickness of the plastic sheet,determine:
$(i)$ The area of the sheet required for making the box.
$(ii)$ The cost of the sheet for it,if a sheet measuring $1\, m^2$ costs $Rs. 20$.

$A$ cylindrical pillar is $50 \, cm$ in diameter and $3.5 \, m$ in height. Find the cost of painting the curved surface of the pillar at the rate of $Rs. \, 12.50$ per $m^2$. $\left[ \text{Assume } \pi = \frac{22}{7} \right]$

The surface area of a cube whose edge is $a$ is: (in $a^{2}$)