The purpose of this study is to construct and evaluate diagnostic battery tests of verbal and non-verbal learning disabilities for students in the Arabic schools. 612 students were in the 3rd, 4th and 5th grades of primary school were involved, mostly from Egypt and Saudi Arabia. Their ages ranged from 7.94-10.98 with mean age = 9.62 and SD =…

Background: In the last decades, children's understanding of mathematical principles has become an important research topic. Different from the commutativity and inversion principles, only few studies have focused on children's understanding of the addition/subtraction complement principle (if a - b = c, then c + b = a), mainly relying on verbal…