Find the surface area of a sphere of diameter $21 \, cm$. Assume $\pi = \frac{22}{7}$. (in $, cm^{2}$)

Hameed has built a cubical water tank with a lid for his house,with each outer edge $1.5\, m$ long. He gets the outer surface of the tank,excluding the base,covered with square tiles of side $25\, cm$ (see figure). Find how much he would spend on the tiles,if the cost of the tiles is $Rs. 360$ per dozen.

Find the capacity in litres of a conical vessel with height $12 \,cm$ and slant height $13 \,cm$.

The radius of a spherical balloon increases from $7 \, cm$ to $14 \, cm$ as air is being pumped into it. Find the ratio of surface areas of the balloon in the two cases.

Find the cost of digging a cuboidal pit $8 \, m$ long,$6 \, m$ broad,and $3 \, m$ deep at the rate of $Rs. 30$ per $m^3$.

The capacity of a cuboidal tank is $50000$ litres of water. Find the breadth of the tank,if its length and depth are respectively $2.5\, m$ and $10\, m$. (in $, m$)