If the radius of a sphere is doubled,then its volume is increased by (in $\%$)

$A$ rectangular tank is $30\,m$ long and $20\,m$ broad. Water is being flown into it through a square pipe of side $5\,cm$. What is the speed of water if the level of water in the tank rises by $1\,m$ in $8\,hours$? (in $km/h$)

$A$ cylindrical iron rod is $70\, cm$ long. The diameter of its end portion is $2\, cm$. What is its weight,reckoning a $cm^3$ of iron to weigh $10\, grams$? (in $kg$)

The perpendicular height of a conical tent is $4 \frac{2}{3} \text{ m}$ and the diameter of its base is $6 \text{ m}$. If $11$ persons can sleep in this tent,find how many average cubic meters $(m^3)$ of air each person gets?

How many cubes of $10\, cm$ edge can be put in a cubical box of $1\, m$ edge?

Find the curved surface area (in $cm^{2}$) of a hemisphere of diameter $28\, cm$.