This study focuses on a computer-based training program in inductive reasoning through tasks embedded into mathematical content for 9-11-years-old students (N = 118) and presents the results of the evaluation study. The online training consists of 120 playful problems based on Klauer's "Cognitive training for children" concept and on his theory of inductive reasoning (Klauer, 1989). Both the experimental and the control group in the study consisted of 118 participants. A computer-based inductive reasoning test comprising of 44 multiple-choice items was used in the pre- and posttest to measure the effectiveness of the training (Cronbach alpha = .91). Both the test and the training tasks were in Arabic context regarding language and used directions and were delivered via the eDia online assessment platform (Csapo & Molnar, 2019). On the posttest, after the six weeks of training the experimental group significantly outperformed the control group by more than one standard deviation. The effect size of the training was in international context high (Cohen d = 1.71). Non-significant variance of the latent slope indicated that there was no significant variability in responding to the intervention program. This study provided evidence that inductive reasoning could be developed even on class level and in a computerised environment very effectively at the age of 9-11 independent of students' original level of inductive reasoning, school-achievement, gender, and socio-economic status.