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 $Rs.$):

Three solid spheres have their radii $r_{1}, r_{2}$ and $r_{3}$. The spheres are melted to form a single solid sphere of a bigger radius. The radius of the new sphere is:

$A$ circus tent is cylindrical to a height of $3\, m$ and conical above it. If its diameter is $105\, m$ and the slant height of the conical portion is $53\, m$,calculate the length of the canvas $5\, m$ wide required to make the tent. (in $m$)

The radius of the base of a hollow cone is $8\, cm$ and its height is $15\, cm$. $A$ sphere of the largest possible radius is placed inside the cone. What is the ratio of the radius of the base of the cone to the radius of the sphere?

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

$2$ cubes,each of side $12\, cm$,are joined end-to-end. The surface area of the resulting cuboid is...........$cm^2$.