Describes a study designed to investigate the relationship between students' learning of the standard double-digit addition algorithm and basic fact mastery or numeration concepts. Results suggest basic fact mastery and knowledge of numeration concepts may not be as necessary as previously assumed to learning multidigit addition. (PK)

The study investigated which addition facts children and preservice teachers view as being difficult, whether it is possible to determine facts which are difficult for all children, and whether children and adults agree on which facts are difficult. Results indicated that children and adults disagree about the difficulty of facts. (PK)