Task# To regroup or not to regroup

Illustrative MathematicsVaries

In a typical subtraction task where students have learned and are using the standard US algorithm, we present a variety of problems that require regrouping in different places and ask students to solve them. This task presents an incomplete problem and asks students to choose numbers to subtract (subtrahends) so that the resulting problem requires different types of regrouping. This way students have to recognize the pattern and not just follow a memorized algorithm. This task is appropriate to use after students have learned the standard US algorithm.