The development in mathematical flexibility should be included in the mathematics teaching training of students in Primary Education Degree. Teachers in training have to acquire the skill to modify the problem resolution and be able to break with stereotyped methods. This document presents an analysis of spontaneous mathematical flexibility developed by teachers in training against problems in which the calculation of the area is requested. At the same time what type of statement can promote is analysed, in a more effective way, a flexible thought and the comparison of the possible mathematical flexibility between the different problems is established.