五年制小学数学第九册第四章第三小节,学习百分数的三类基本题及其扩张类型的应用题。这三类百分数应用题的基本数量关系式是:比较量÷标准量=百分率;标准量×百分率=比较量;比较量÷百分率=标准量。学生在解题过程中,往往由于搞乱了标准量和比较量而列错了算式。为了解决这个问题,可运用变的方法进行教学,使学生在交中求不变,进而掌握规律,提高解题能力。第一类应用题的“鼍变”—— Five-year elementary school mathematics ninth chapter fourth chapter third subsection, the three basic types of learning percentage and the application of the expansion type. The basic relationship between these three types of application questions is the amount of quantity: standard ÷ standard = percentage; standard × percentage = comparison; comparison ÷ percentage = standard. Students in the process of solving problems, often mess with the standard amount and comparison of the wrong formula. In order to solve this problem, we can use different methods to teach, so that students can not change while they pay, so as to grasp the law and improve the ability to solve problems. The first application of the “change” -