The total surface area of a cube is $216 {\mathrm{cm}}^2$, find its volume.

Four cubes, each of edge $9 \mathrm{cm}$ are joined as shown bellow:

Write the dimensions of the cuboid obtained. Also total surface area and volume.

How many persons can be accommodated in a big hall of dimensions $40\mathrm{ }\mathrm{m},\mathrm{ }25\mathrm{ }\mathrm{m}$ and $5 \mathrm{m}$ assuming that each person requires $5 {\mathrm{m}}^3$ of air?

The dimensions of a classroom are, length $=15 \mathrm{m}$, breadth $=12 \mathrm{m}$ and height $=7.5 \mathrm{m}$. Find, how many children can be accommodated in this class-room, assuming $3.6{ \mathrm{m}}^3$ of air is needed for each child.

The length, breadth and height of a room are $6 \mathrm{m}, 5.4 \mathrm{m}$ and $4 \mathrm{m}$, respectively. If the area of its four walls is $k {\mathrm{m}}^2$ in a decimal number, find $k$.