Background: In the last decades, children's understanding of mathematical principles has become an important research topic. Different from the commutativity and inversion principles, only few studies have focused on children's understanding of the addition/subtraction complement principle (if a - b = c, then c + b = a), mainly relying on verbal…

Examines the scope and nature of upper elementary school pupils' difficulties with modeling and solving nonroutine additive word problems. Concludes that many errors result from the superficial, stereotyped approach of adding or subtracting two given numbers without considering the appropriateness of that action in relation to the problem context.…