Authentic context is a physical environment reflecting the knowledge application in the real world. In this study, we developed a tablet-based application, Ubiquitous Fraction (U-Fraction), to help fractions learning with authentic contextual support. Three topics were designed to learn fractions concept, fractions simplification, and fractions addition/subtraction. The learning achievement was evaluated by three variables: understanding fraction and fraction representation to evaluate fractions concept and fractions simplification, and problem solving to evaluate the three topics. This study used two groups of experimental research. The experimental group (EG) learned fractions using U-Fraction in authentic contexts, while the control group (CG) learned fractions using the traditional teaching method and paper-based assignment. The results showed that EG significantly outperformed CG. Furthermore, it was found that learning behaviors of EG had significant correlation among quantity of assignment, annotations of assignment, and post-test. Two assessment mechanisms, peer and teacher assessments using scaffoldings based on multiple representations (i.e., linguistic, logic mathematics, and visual representation), were employed to help assessment and improve the assessment results. It was found that the scaffoldings can help both peer and teacher assessments, which significantly correlated with post-test. Therefore, multiple representations and scaffoldings were helpful to improve students' learning and peer assessment. Students also perceived positively toward using U-Fraction in terms of usefulness, ease of use, ease of learning, and satisfaction of the usability questionnaire. These imply that fraction learning should be designed in a way that students can apply their knowledge in authentic contexts by taking pictures and making multiple representations.