Strategies for addition and subtraction in the range 1 to 100 of adolescents attending a special school for the intellectually disabled in Indonesia

The study focuses on the strategies used by adolescents with intellectual disabilities in solving addition and subtraction problems in the range 1 to 100. The epistemological basis for this investigation is radical constructivism. Data were collected through video-recorded clinical interviews and individual teaching experiments. The data analysis showed that counting strategies involving fingers, toes or gestures were frequently used by adolescents with mild intellectual disabilities, even though they were familiar with standard written algorithms. It suggests that a specific framework that incorporates the use of fingers, toes and gestures is needed for explaining these strategies.