The volume of a cylinder is $550 \, cm^3$ and its radius is $5 \, cm$. Then,its height is ....... $cm$.

The radii of two $10 \, cm$ high metallic cylinders are $3.5 \, cm$ and $7 \, cm$. These cylinders are melted and recast to produce a cylinder with height $50 \, cm$. Find the radius of this new cylinder (in $cm$).

The $CSA$ of a cone with radius $7\, cm$ and slant height $15\, cm$ is $\ldots \ldots \ldots \, cm^2$.

The radius of a cone is $15 \, cm$ and its base is hemispherical. If the total height of the solid is $55 \, cm$,find its volume in $cm^3$.

$A$ plumbline (sahul) is the combination of (see figure):

$CSA$ of a hemisphere with diameter $20 \, cm$ is $\ldots \ldots \ldots cm^{2}$. (in $\pi$)