to get the perfect solution to the problem, all possibilities must be tried. this is often not a good option, as trying them takes a long time, and on average, half the possibilities must be tried until a solution is found. so what most people will do is to start with the biggest item, fit it in, and then try to arrange the other items around it. this will give a good solution, most of the time. there are cases however, where such a solution is very bad and another technique must be used.