$A$ hall is $15 \ m$ long and $12 \ m$ broad. If the sum of the areas of the floor and the ceiling is equal to the sum of the areas of the four walls,the volume of the hall is: (in $m^3$)

$A$ cylindrical vessel of radius $4 \, cm$ contains water. $A$ solid sphere of radius $3 \, cm$ is lowered into the water until it is completely immersed. The water level in the vessel will rise by (in $cm$)

$3$ cubes of metal whose edges are in the ratio $3: 4: 5$ are melted into a single cube,the length of whose diagonal is $48 \sqrt{3} \text{ m}$. Calculate the edges of the three cubes.

If the radius of a sphere is doubled,then its surface area is increased by (in $\%$)

$A$ tent is in the shape of a right circular cylinder up to a height of $3\, m$ and then becomes a right circular cone with a maximum height of $13.5\, m$ above the ground. If the radius of the base is $14\, m$,find the cost of painting the inner side of the tent at the rate of ₹ $2$ per $m^2$ (in ₹).

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?