This paper describes use of an online Student Response System (SRS) in a pre-qualification course for engineering studies in Norway. The SRS in use, where students answer quizzes using handheld mobile devices like Smartphones, PADs, iPods etc., has been developed at Sor-Trondelag University College. The development of the SRS was co-funded by the Lifelong Learning Program KA3-ICT in 2009-2010. SRS has been designed to help teachers effortlessly i) break the monotony of a lecture and allow the students to actively take part in the lecture, ii) increase teacher-student interaction, and iii) give teacher and students immediate anonymous feedback on learning outcome. The response system was used in mathematics in two groups with different lecturers during two semesters in 2009-2010. The pedagogical methods in use will be referred to as "Peer Instruction" and "Classic". In each method the students will answer a multiple choice quiz using their mobile devices. In both cases the result of the quiz will immediately appear as a histogram on a screen in the classroom. The closing parts will also be identical. The lecturer then highlights the correct option in the histogram and explains why this option actually is the correct one. In the Peer Instruction method there will be an additional element. The first poll will be followed by a discussion in student groups, where the students are urged to defend their choice and convince their fellow students that their chosen option is the correct one. The discussion is then followed by a new individual voting session before the final results are shown and the closing part takes place. The paper will compare this method with the peer instruction method as described in existing literature. The learning outcome will be discussed according to interviews with students and the lecturers' experiences from the classroom. In addition we will analyze students' grades and test results in mathematics with respect to their expected level, based on previous achievements. We will present results showing that when students are arguing their point of view, they will have a stronger tendency to convince their fellow students when they themselves already have found the correct option in the quiz. Finally we will suggest pedagogical improvements for future use of response systems in mathematics. Input from lecturers and from students has already been used in the process of developing a new version of SRS, finished in January 2013.