“两位数乘两位数”教学的难点是让学生理解算理,在平时的计算教学中,我们教师常常会忽视算理的教学。其实,透彻理解算理是熟练掌握算法的前提,是提高学生计算能力的重要保证。我采用同课异构的方式,探寻“两位数乘两位数”的有效教学方式,让学生经历竖式形成的过程,强调和深化学生对算理的理解。经过实践,我觉得借助直观模型、拆数法和已有知识,可以明显地促进学生对算理的理解。一、依托直观模型,促进对算理的理解 “Double digits by two digits ” The difficulty of teaching is to enable students to understand arithmetic, teaching in the usual calculation, we teachers often ignore the teaching of arithmetic. In fact, a thorough understanding of arithmetic is a prerequisite for mastering the algorithm, and an important guarantee for improving students’ computing abilities. I use the same way heterogeneous class to explore “double-digit by two digit ” effective teaching methods, so that students experience the process of vertical formation, emphasize and deepen students’ understanding of arithmetic. After practice, I think that with the aid of visual models, demolition methods and existing knowledge, we can obviously promote students’ understanding of arithmetic. First, relying on the intuitive model to promote the understanding of arithmetic