Solving Subtraction Problems by Means of Indirect Addition

Subtraction problems of the type a – b = ? can be flexibly solved by various strategies, including the indirect addition strategy ("how much do I have to add to b to get at a?"). Little research has been done on the use of the indirect addition strategy with multi-digit numbers. The present literature review entails a summary of three recent and closely related studies conducted by the authors on this issue. The results of our first study revealed that young adults efficiently and flexibly applied indirect addition on 3-digit subtractions. The results of our second and third study showed that elementary school children seldom used indirect addition on 2-digit subtractions, despite its computational efficiency. This held true even in children who received school-based instruction in the strategy. We end with a discussion of some theoretical, methodological, and educational implications of the studies being reviewed.