8. Example data, the condition. Hence, the teacher can seldom afford. to miss the questions: What is the unknown? are Whui the data? What is the condition? The student should consider the principal parts of the problem attentively, repeatedly, and from various sides. If there is a figure connected with the problem he should draw a figure and point out on it the unknown and the data. If it is necessary to give names to these objects he should introduce suitable notation; devoting some atten- tion to the appropriate choice of signs, he is obliged to consider the objects for which the signs have to be chosen There is another question which may be useful in this preparatory stage provided that we do not expect a definitive answer but just a provisional answer, a guess: 's it possible to satisfy the condition? (In the exposition of Part II [p. 88) "Understanding he problem" is subdivided into two stages: "Getting ac-