For me, it’s easier to understand by first dividing by the lower number and then multiplying by the higher number. Even though the order doesn’t matter as they give the same result, at least it shows the logic that the 4cm height is divided into 9 chunks that are each 0.4cm (4/9) high. Since that is also their width, you multiply it by 16 chunks to get a width of 7.1.
