The present study aimed to evaluate the nature of knowledge construction (abstraction) during the learning process related to multiplication of fractions. For this purpose, an activity designed in accordance with the RBC + C (Recognizing - Building with Construction and Consolidation). The model was carried out with two high achieving fourth graders. At the end of the study, it was observed that students participating in the case study successfully used all epistemic actions included in the RBC + C and they managed to reach formal level about fractional multiplication. (C) 2015 The Authors. Published by Elsevier ltd.