Objective: The purpose of present research was the comparison of the effectiveness of cognitive & cognitive-metacognitive strategies based on mathematical problem-solving skills on 9th grade girl students with intellectual disability in Tehran Province.

Materials & Methods: The research is an experimental, comparing pre-test and post-test data. The participants were chosen by cluster sampling from three schools three districts of Tehran Province (Gharchak, Shahrerey and Shahryar). Fifteen female students with Intellectual disability were assigned from each school and they were divided into three, one control and two experiment groups. For experimental groups students cognitive & cognitive-metacognitive strategies were taught in the 15 instructional sessions, but the control group students did not receive none of strategies in the same sessions. The instruments consist of Wechsler intelligence test was used for matching the groups in terms of IQ, a teacher performed the tests for mathematical problem-solving and instructional pakage of cognitive and cognitive-metacognitive strategies. The data analysis was done by using descriptive statistics (mean, standard deviation and frequency table) and ANCOVA.

Results: The findings of this research showed that there was significant increasing in mathematical problem-solving skills in the group receiving cognitive-metacognitive strategies in comparison with the cognitive group (P<0.005) and control group (P<0.001). Beside, the mean difference of the cognitive group was significantly more than the control group (P<0.003).

Conclusion: The mathematical problem-solving skill of the students have been improved through cognitive-metacognitive and cognitive strategies. Also, the instruction of cognitive-metacognitive strategies, in compared with cognitive strategy caused more improvement on the performance of mathematical problem-solving skills.