This study investigated proportional reasoning and the related concepts of decimal, percent, and ratio. In particular, the research focused on analyzing the gaps and understandings that grades 6, 7, and 8 students have and advanced factors for such gaps and understandings. The study employed a mixed method approach in which quantitative data was collected and analyzed in the first phase. The hypothesis that differences in mean performance of students on the test among grades 6, 7, and 8 would be statistically significant was not supported by the data. The second phase involved collection of qualitative data, specifically interviews and documents observation. The interview data revealed that several factors relating to the learner, task, and strategy were responsible for the gaps and understandings. Implication for planning, instruction, and assessment is discussed.