In the auditorium,there are $20$ cylindrical pillars. Each pillar has a radius of $14 \, cm$ and a height of $5 \, m$. Find the cost of painting the curved surface of all the pillars at the rate of ₹ $120$ per $m^2$.

In $\triangle ABC$,$\angle B = 90^{\circ}$,$AB = 28 \, cm$,and $BC = 21 \, cm$. If the triangle is revolved about the side $AB$,find the curved surface area of the cone so obtained. Similarly,if the triangle $ABC$ is revolved about the side $BC$,find the curved surface area of the cone so obtained.

$A$ metallic ball of radius $9 \,cm$ is melted and recast into three metallic balls. If the radii of two balls are $1 \,cm$ and $6 \,cm$,find the radius of the third ball (in $cm$).

$A$ storage tank is in the form of a cube. When it is full of water, the volume of water is $15.625 \, m^3$. If the present depth of water is $1.3 \, m$, find the volume of water already used from the tank (in $m^3$).

Find the surface area of a sphere of diameter $3.5\,m$ (in $m^2$).

State whether the following statement is true or false:
The radius of a cone can be $3 \, cm$,slant height $4 \, cm$,and height $5 \, cm$.