The curved surface area of a cone is $550 \, cm^2$. If the radius of the cone is $7 \, cm$,find its volume in $cm^3$.

Find the curved surface area and the total surface area of a hemisphere with a diameter of $2.8\,m$.

Find the curved surface area,total surface area and volume of a hemisphere of diameter $42\, cm$.

State whether the following statement is True or False and justify your answer:
$A$ cone,a hemisphere,and a cylinder stand on equal bases and have the same height. The ratio of their volumes is $1: 2: 3$.

$A$ conical tent is made from a piece of cloth with an area of $165 \, m^{2}$. The radius of the base of the tent is $5 \, m$.
$(i)$ If one student occupies an average of $\frac{5}{7} \, m^{2}$ of ground area,how many students can sit in the tent?
$(ii)$ Find the volume of the cone.

The radii of three metal spheres are $3 \,cm, 4 \,cm$ and $5 \,cm$ respectively. They are melted into a single solid sphere. Find the radius of the new solid sphere (in $cm$).