$A$ metallic sphere of radius $21 \,cm$ is melted and recast into a wire with radius $0.5 \,cm$. Find the length of the wire in metres.

$A$ metallic cylinder with diameter $1 \, cm$ and height $4 \, cm$ is melted and recast to produce balls of radius $\frac{1}{8} \, cm$. Find the number of balls produced.

$A$ cistern,internally measuring $150 \,cm \times 120 \,cm \times 110 \,cm$,has $129600 \,cm^3$ of water in it. Porous bricks are placed in the water until the cistern is full to the brim. Each brick absorbs one-seventeenth of its own volume of water. How many bricks can be put in without overflowing the water,each brick being $22.5 \,cm \times 7.5 \,cm \times 6.5 \,cm$?

$A$ solid piece of iron in the form of a cuboid of dimensions $49 \, cm \times 33 \, cm \times 24 \, cm$ is moulded to form a solid sphere. The radius of the sphere is (in $cm$):

$1\,m^3 = \dots \dots \dots cm^3$.

$A$ cone and a cylinder have equal radii and equal heights. Then,the ratio of their volumes is $\ldots \ldots \ldots . .$