In this Montessori inspired regrouping activity, students use the movable base ten blocks provided to regroup 100s and write the simplified number of blocks in standard form. This activity is self-checking as all good Montessori-inspired materials should be. It contains TEN regrouping tasks in a fun aqua colored theme. Students can check their own work using the answer key provided, or the teacher can delete the answer key ahead of time and check student work themselves. This activity is part of a series of basic regrouping activities that are part of the Montessori Exchange Game.