This thesis deals with introducing the concept of perimeter of a rectangle to maths lessons in elementary education, specifically by using discovery learning as a fundamental technique in modern teaching. Firstly, basic geometry terms of perimeter and rectangle are briefly described, followed by an overview of discovery learning from pedagogical and mathematical point. Furthermore, concept of perimeter was approached with the current curricular documents in mind: Curriculum and Syllabus, National Curriculum Framework, suggested curricular reform; as well as with current textbooks for the fourth grade of primary school. For this thesis’s purposes, an online survey was conducted amongst students of Faculty of Teacher Education, in order to assess opinions on geometry and amount of geometry lessons in mathematics. The online survey is described in detail and it shows that students prefer for geometry lessons to be presented using real-life examples. Moreover, a classroom intervention was made, where pupils approached these concepts of rectangle perimeter and square perimeter by means of differentiated, creative tasks and different didactic materials. Lessons were based on discovery learning; including high-level activity of pupils in class and examples related to common everyday situations. To determine the effectiveness of those methods, pupils have completed the survey at the end of the lessons.