单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,万以内的加法和减法,1,教学目标,1.,知识与技能：通过观察,找到两个算式之间的联系与区别,.,2.,过程与方法：再通过计算,发现两个算式的积相等,.,从而引发大家的好奇心,激发大家探索规律的迫切欲望,体验数学活动充满着探索与创新,.,3.,情感、态度和价值观：使大家学习一些数学中的规律,激发对数学的喜爱,增强学习数学的兴趣,.,2,两位数加、减两位数,几百几十加、减几百几十,加、减法的估算,3,例,1,64,25=,方法一,6 4,2 5=,60,4,20,5,80,9,89,8 9,方法二,6 4,2 5=,20,5,84,89,8 9,89,4,例,1,64,25=,方法三,方法四,6 4,2 5=,60,4,85,89,8 9,6 4,2 5=,20,5,69,89,8 9,89,5,例,2,72,49=,23,方法一,72,40,32,32,9,23,72,50,22,22,1,23,方法二,6,例,2 72,49=,23,方法三,方法四,72,9,63,63,40,23,52,9,3,20,3,23,7,例,2 72,49=,23,方法三,方法四,72,9,63,63,40,23,52,9,3,20,3,23,返回,8,例,3,650,340,方法一,方法二,600,300,900,50,40,90,65,34,99,650,340,990,900,90,990,990,9,例,4,840,560,方法一,方法二,840,500,340,340,60,280,84,56,28,840,560,280,280,10,360,710,220,+280,490,800,320,270,640,990,500,220,530,50,练一练,11,360,710,220,+280,490,800,320,270,640,900,500,220,530,50,练一练,返回,12,382,246,693,381,502,198,786,335,155,452,337,241,估算下面算式的结果：,大约得,600,大约得,450,大约得,300,大约得,600,大约得,100,大约得,700,13,349,226,258,171,720,112,106,438,419,201,525,239,619,203,864,243,先估算结果,再分类：,比,500,大,比,500,小,14,先估算结果,再分类：,349,226,258,171,620,1,25,106,438,419,201,525,239,619,203,864,243,比,500,大,比,500,小,15,59,元,40,元,38,元,62,元,妈妈有,100,元,想买一套儿童服装,妈妈可以怎样买？,16,买法一,59,元,40,元,59,40,99,（元）,17,买法二,62,38,100,（元）,38,元,62,元,18,买法三,59,38,97,（元）,59,元,38,元,19,本课小结,通过学习使同学们学会几千几百加、减整千或整百的口算方法,.,理解只有相同数位上的数才能相加减的道理,为万以内数的计算打好基础,.,20,