Volume of the cylinder is $1650\, m^3$,whereas the surface area of its base is $78 \frac{4}{7}\, m^2$. Find out the height of the cylinder (in $m$).

Three cubes with sides in the ratio $3:4:5$ are melted to form a single cube whose diagonal is $12\sqrt{3} \text{ cm}$. The sides of the cubes are

$A$ $12\,m$ deep well with internal diameter $3.5\,m$ is dug. The earth taken out from it is spread evenly to form a platform of dimensions $10.5\,m \times 8.8\,m$. Determine the height of the platform in meters. (in $.25$)

What is the length (in metre) of the longest rod that can be placed in a room which is $2$ $metre$ long,$2$ $metre$ broad,and $6$ $metre$ high?

The radius of the base of a solid cone is $9\, cm$ and its height is $21\, cm$. It is cut into $3$ parts by two cuts which are parallel to its base. The cuts are at heights of $7\, cm$ and $14\, cm$ from the base respectively. What is the ratio of the curved surface areas of the top,middle,and bottom parts respectively?

$A$ solid cone of height $36 \, cm$ and radius of base $9 \, cm$ is melted to form a solid cylinder of radius $9 \, cm$ and height $9 \, cm$. What percent of material is wasted in this process (in $\%$)?