The volume of a sphere is $4500 \pi \text{ cm}^3$,then its diameter is $\dots \text{ cm}$.

The radius of a sphere is $2r$,then its volume will be

The front compound wall of a house is decorated by wooden spheres of diameter $21\, cm,$ placed on small supports as shown in the figure. Eight such spheres are used for this purpose,and are to be painted silver. Each support is a cylinder of radius $1.5\, cm$ and height $7\, cm$ and is to be painted black. Find the cost of paint required if silver paint costs $25$ paise per $cm^{2}$ and black paint costs $5$ paise per $cm^{2}.$

Find the surface area of a sphere of diameter $49\, cm$ (in $cm^2$).

Surface area of a sphere $= \ldots \ldots.$

For a given cylinder,the radius of the base is $28 \, cm$ and its height is $90 \, cm$. Find the curved surface area and the total surface area of the cylinder.