A container is made up of a hollow cone with an internal base radius of r сm and a hollow cylinder with the same
base radius and an internal height of 3r cm. Given that
the height of the cone is three-quarters of the height of
the cylinder and 10 litres of water is needed to fill the
conical part of the container completely, find the amount
of water needed to fill the container completely, giving
your answer in litres.​