$1$ hectare $= \ldots \ldots \text{ } m^{2}$

The radii of two cylinders are in the ratio of $2:3$ and their heights are in the ratio of $5:3$. The ratio of their volumes is

Find the total surface area of a hemisphere of radius $42 \, cm$. (in $cm^2$)

The water for a factory is stored in a hemispherical tank whose internal diameter is $14\, m$. The tank contains $50$ kilolitres of water. Water is pumped into the tank to fill it to its capacity. Calculate the volume of water pumped into the tank. (in $, m^{3}$)

In $\Delta ABC$,$\angle B = 90^{\circ}$,$AB = 6.3 \, cm$,and $BC = 8.4 \, cm$. If the triangle is revolved about the side $AB$,find the volume of the cone so obtained. Similarly,if the triangle $ABC$ is revolved about the side $BC$,find the volume of the cone so obtained.

The surface area of a sphere is $2464 \, cm^2$. Find its diameter in $cm$.