KOREAN CHILDRENS SINGLE-DIGIT ADDITION AND SUBTRACTION - NUMBERS STRUCTURED BY 10

Korean children's ability to solve addition problems with sums of 10, single-digit addition problems with sums between 10 and 18, and single-digit subtraction problems with minuends between 10 and 18 was assessed in interviews given at the end of the first semester of first grade, before children had studied problems involving numbers larger than 10 in school. These children showed considerable competence with all three kinds of problems, solving correctly 95%, 85%, and 75% of these problems, respectively. Almost two-thirds of the solutions of the problems above 10 were addition or subtraction recomposition methods structured around ten or known facts. Korean children demonstrated two finger methods that allowed fingers to be reused to show sums over 10. These methods and the regular named-ten Korean number words for numbers between 10 and 18 ("ten, ten one, ten two, ten three,..., ten eight") support Korean children's learning of three efficient recomposition methods structured around ten.