A systems approach provides insight for expanding teachers' pedagogical reasoning for integrating multiple technologies in inquiry, communication, and collaboration. An online learning trajectory supports the integration of a systems pedagogical approach for guiding teachers in developing their technological pedagogical thinking and reasoning so they in turn are able to implement a systems pedagogical approach with their own students. Specific instructional strategies guide teachers in refining their mental models for integrating multiple technologies in teaching mathematics through their increasingly complex technological pedagogical understanding as they learn about the technologies and teaching with those technologies. This study focuses on the impact that a system of multiple technologies as pedagogical tools has on teachers' technological pedagogical reasoning as they integrate multiple technologies in their classrooms. A systems pedagogical understanding is at the core of teachers' enhancement of their technological pedagogical reasoning, and supports the transformation of their knowledge called technological pedagogical content knowledge.