Find the diagonal of a cuboid whose dimensions are $12\, m$ by $10\, m$ by $8\, m$.

If the volume of a sphere is numerically equal to its surface area,then its diameter is ......... $cm$.

The diameter and slant height of a conical tomb are $28\, m$ and $50\, m$,respectively. The cost of whitewashing its curved surface at the rate of $80$ paise per $m^2$ is (in $Rs.$):

If the diameter of a sphere is decreased by $25 \%$,its curved surface area will be decreased by (in $\%$).

If the side of a cube is increased by $100 \%$,its volume is increased by (in $\%$)

$3$ equal cubes are placed adjacently in a row. Find the ratio of the total surface area of the new cuboid to the sum of the surface areas of the three cubes.