Each segment in this series of 17 short videos highlights a different classroom, a different grade level, and the actual demonstration of a particular Mental Math strategy in a specific curricular context. The series is intended to support professional development for teachers who are implementing Mental Math instruction in their classrooms. The series was originally presented on four DVD discs, according to grade level. The fourth DVD simply repeated a sequence of segments (from discs 1-3) across the grade levels, so that viewers may follow the development and amplification of a single Mental Math strategy - these episodes are marked *