The document discusses several studies on teaching ratios and proportions. It finds that symbolic representations can cause difficulties for learning disabled students, while conceptual understanding is stronger. Gender differences did not impact proportional reasoning skills. Instruction should start concretely and develop multiplicative thinking over time. Allowing students to manipulate objects and verbalize their thinking deepens understanding. Students can develop their own successful problem-solving strategies. Discovery learning and group work improves comprehension more than direct instruction. Implementing brief vocabulary reviews improved student performance. Developmental differences in proportional reasoning are not based on age. Teachers also lack full understanding of proportions and strategies for teaching the concept.