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

$A$ hemispherical tank is made up of an iron sheet $1 \,cm$ thick. If the inner radius is $1 \,m$,then find the volume of the iron used to make the tank. (in $,m^3$)

If the volume of a right circular cone of height $9 \, cm$ is $48 \pi \, cm^3$,find the diameter of its base. (in $, cm$)

The height of a cone is $15 \, cm$. If its volume is $1570 \, cm^3$,find the radius of the base. (Use $\pi = 3.14$) (in $, cm$)

$A$ plastic box $1.5\, m$ long,$1.25\, m$ wide,and $65\, cm$ deep is to be made. It is opened at the top. Ignoring the thickness of the plastic sheet,determine:
$(i)$ The area of the sheet required for making the box.
$(ii)$ The cost of the sheet for it,if a sheet measuring $1\, m^2$ costs $Rs. 20$.

Find the volume of the right circular cone with radius $3.5 \, cm$,height $12 \, cm$. Assume $\pi = \frac{22}{7}$. (in $, cm^3$)