The surface area of a sphere is $7850 \, cm^2$. Find its radius in $cm$. (Use $\pi = 3.14$)

The radius of a sphere is increased by $10 \%$. Prove that the volume will be increased by $33.1 \%$ approximately.

Find the surface area of a sphere of radius $30 \, cm$ $(\pi = 3.14)$ (in $cm^2$).

Rain water which falls on a flat rectangular surface of length $6\, m$ and breadth $4\, m$ is transferred into a cylindrical vessel of internal radius $20\, cm$. What will be the height of water in the cylindrical vessel if the rainfall is $1\, cm$? Give your answer to the nearest integer. (Take $\pi = 3.14$) (in $cm$)

Find the surface area and volume of a sphere of diameter $28 \, cm$.

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