inquiry-based learning; mistake; equality relation; rounding; decimal notation

Mathematics is a subject with perhaps the greatest overlap with other fields, especially the natural sciences. As a secondary e˙ect of a project focused on creating and piloting problem tasks in the field of chemistry and physics, utilizing inquiry-based learning, we observed the most common mathematical mistakes and conceptual errors that are made by students using mathematical knowledge in other areas of the natural sciences. A total of 40 problem tasks were created and verified in cooperation with secondary-school teachers of physics and chemistry and more than 650 solutions by student were qualitatively assessed. The paper will present the most common mistakes and errors repeated across all tasks and compare their occurrence between teachers who have and do not have mathematics as a secondary subject. The mistakes and errors will also be explained from a mathematical point of view and a proposal will be outlined on how to innovate the teaching of mathematics in secondary schools. This should lead to the correct understanding of the issues and the elimination of the errors found by this research.