There is a basic difference between the concept of "problem" and "exercise". Not the same do an exercise to solve a problem. One thing is to apply an algorithm in a more or less mechanically, avoiding the difficulties introduced by the application of increasingly complex rules, and another, solving a problem, give a coherent explanation for a set of related data in context. The answer is usually single, but the strategy is determined by factors resolute maturation or otherwise. The problem solving strategy is much richer than the mechanical application of an algorithm; it involves creating a context ...