教材分析本节课取材于北师大版数学教材第四册,教学的主要目的是:借助实际情境学习估算的一般方法,逐步养成良好的估算意识,提高估算能力;在“买东西”的活动中,经历估算的应用,交流各自的估算策略,比较各自的估算结果,体验数学与生 Teaching material analysis This lesson is drawn from the fourth edition of the mathematics textbook of Beijing Normal University. The main purpose of teaching is: to gradually develop a good sense of estimation and improve the estimation ability by means of the general method of actual situation learning estimation; Activities, experience estimated applications, exchange their own estimation strategies, compare their estimates, experience math and students