In this paper we present the results of an experiment made with our e-librarian service ”MatES”, an e-Learning tool on fractions in mathematics. MatES allows students to enter complete questions in natural language and returns semantically pertinent multimedia results which explain the answer to the users’ question. The efficiency of MatES was proven by benchmark tests. From 229 different user questions, the system returned the right answer for 97% of the questions, and only one answer (the best one) for nearly half of the questions. A class of 22 students took part in the five week experiment. Students were autonomous and learned through exploratory exercises. Students asked MatES questions. The multimedia explanations yielded by MatES allowed to acquire new knowledge, and to complete the exercises. At the conclusion of the experiment, MatES was confirmed as an efficient e-librarian service that can be used in school or at home. It can be used in blended learning, distance l...