Abstract
Fifteen junior high school students with intellectual disabilities (<7 mental age) participated individually in an experiment in which they were given a task related to number concepts and equal distribution. The main results were as follows: (1) Number concepts of students with intellectual disabilities closely corresponded to students' mental age regardless of their chronological age. However, the way they solved problems was different from that of children without intellectual disabilities. (2) Some students had simple computational skills even though their mental ages and number concepts were both at an early childhood stage. (3) With increased mental age, children became better at the equal distribution task. (4) There was a difference in distributive strategies depending on the child's number concept. These findings suggest that children with intellectual disabilities learn informal mathematical skills in a unique way.
