Mathematics becomes more indispensible course today, while it seems approaching to the middle school students as a boring and hard one. So, we need to take more motivational teaching devices as well as mere emphases on its importance in order to keep the students up to tile curriculum and improve the education efficiency. Then, history of mathematics call lie one major source of the motivation, since, by telling the tales on the specific unit subject, teachers can awake the students'interest naturally. Today, most of the mathematics textbooks for the middle school students have some historical tales about each unit subject in their respective unit introduction. However, many tales don't seem quite helpful or motivating to understand unit subjects, for they are either abstract or fragmental. In that sense, this paper has three sample guidelines for teaching, which ate meant to introduce historical tales to motivate the students before teachers may get into tile main unit subject. Those suggested in this paper may work as the motivational teaching devices which would make the students mote interested, more positive, and consequently more successful in mathematics.