The ratio of the diameters of two cylinders is $3:4$ and the ratio of their heights is $4:5$. Then,the ratio of their volumes is ..... .

Three metallic solid cubes whose edges are $3 \, cm$,$4 \, cm$,and $5 \, cm$ are melted and formed into a single cube. Find the edge of the cube so formed (in $cm$).

The $CSA$ and the volume of a cylinder are numerically equal. Then,its radius is $\ldots \ldots \ldots \ldots$ units.

How many cubic centimetres of iron are required to construct an open box whose external dimensions are $36 \, cm$,$25 \, cm$,and $16.5 \, cm$,provided the thickness of the iron is $1.5 \, cm$? If one cubic $cm$ of iron weighs $7.5 \, g$,find the weight of the box.

The earth dug out by digging a well with diameter $5.4 \, m$ and depth $20 \, m$ is uniformly spread on a circular ground with radius $15 \, m$. Find the increase in the level of the ground in $cm$.

The radii of three metallic spheres are $3 \, cm$,$4 \, cm$,and $5 \, cm$. These spheres are melted and recast into a single new sphere. Find the radius of the new sphere (in $cm$).