How many coins,$2 \, mm$ thick and $1.5 \, cm$ in diameter,should be melted in order to form a right circular cylinder with base diameter $6 \, cm$ and height $8 \, cm$?

$A$ solid cylinder has a total surface area of $462 \, cm^2$. Its curved surface area is $\frac{1}{3}$ of its total surface area. The volume of the cylinder is.......$cm^3$.

$A$ rectangular water tank is $80 \, m \times 40 \, m$. Water flows into it through a pipe with an opening area of $40 \, cm^2$ at a speed of $10 \, km/h$. By how much will the water level in the tank rise in half an hour (in $cm$)?

If the length,breadth and height of a rectangular parallelopiped are in the ratio $6:5:4$ and if the total surface area is $33,300\, m^{2}$,then the length,breadth and height of the parallelopiped (in $m$) respectively are:

If a sphere of radius $r$ is divided into $4$ identical parts,then the total surface area of the $4$ parts is

The height and base radius of a cone are each increased by $100 \%$. The volume of the cone now becomes