新课标四年级小数加减法简便运算例4.ppt

数学第八册,小数加减法简便计算例4,一、复习,用简便方法计算下面各题。（1）3612575（2）48855215（3）460176124,从这幅图中得到哪些信息？,要求的问题是什么？,怎么计算?,8.428.468.548.58,=16.888.548.58,=25.428.58,=34（秒）,8.428.468.548.58,=（8.428.58）（8.468.54）,=1717,=34（秒）,答:可能的总成绩是用了34秒.,应用了加法交换律和结合律.,三、巩固,3.3,1.38,1.75,0.25,（1）,（2）,（3）,（4）,3、口算0.340.45=,0.79,0.570.9=,1.47,3.80.12=,3.92,1.30.7=,0.6,84.6=,3.4,0.60.37=,0.23,4、简便计算.0.3840.362.64 5.263.430.741.293.70.716.3 3.94.083.921.1,5、看谁想得快,怎样简便就怎样算.5.62.74.4 9.141.434.579.54.856.13 772.72.32510.750.49.86 51.278.661.34,作业,1、在 里填上适当的数。,(1)3.84.756.2=3.8 4.75,(2)2.765.5514.45=(),(3)0.67.913.40.09=()(),2、计算下面各题,怎样简便就怎样计算。,2.850.475.15 8.325.470.53,4.082.795.92 14.52.752.52.25,4.80.74.80.7 4.765.872.76,