Abstract
This paper reports on a longitudinal study across YeMS 2 and 3 of 104 childrenfs petfonnance and strategy use for two-digit separation and missingaddend word problems and vertical and horizontal algorithmic exercises with and without regrouping. The study showed that while Year 2 children predominantly used a subtractive removing strategy for separation problems and an additive building-on strategy for missing-addend problems, Year 4 children were more mixed in their strategy use. It also showed that children used subtractive strategies predominantly for vertical and horizontal algorithmic exercises.