A metal sphere of radius 15cm is melted down and recast into a solid cylinder of radius 6cm. Calculate the height of the cylinder.

Using the eqauation for volume of sphere (V=4/3 pi r^3) calculate the volume of the original sphere. This comes to 14137.2 cm^3 (1dp). The new cylinder formed has the same volume. Therefore, you can use the equation for volume of cylinder (V=pi r^2 h) to calculate the height, by rearranging the equation to make h the subject.

This gives you an answer of 125cm