5.8 积的小数位数不够的小数乘法.pptx

,积的小数位数不够的小数乘法,情景导入,探究新知,课堂小结,课后作业,小数乘法和除法,课堂练习,5,情景导入,6.70.3=,6.70.3,1,先按整数乘法算出积,67 3,1,一位小数,一位小数,两位小数,.,再看因数中一共有几位小数就从积的右边起数出几位，点上小数点。,2 0 1,.,0,2,0,2,九折,探究新知,例 1,小明在阳台上摆放了一个花架，它的底边是边长0.28米的正方形。这个花架的占地面积是多少平方米？,0.280.28（平方米）,要从积的右边起数出几位点上小数点？位数不够怎么办？,0.2 8 0.2 8 2 2 4 5 6 7 8 4,小明在阳台上摆放了一个花架，它的底面是边长0.28米的正方形。这个花架的占地面积是多少平方米？,0.0784,答：花架的占地面积是 平方米。,0.280.28（平方米）,0.0784,在积里点小数点时，位数不够的，在前面用0补足。,0.2 8 0.2 8 2 2 4 5 6 7 8 4,0,.,0,练一练,你能给下面各题的积点上小数点吗？,0.7 0.9 6 3,1.0 5 0.0 6 6 3 0,0.1 8 0.3 5 4,.,.,.,0,0,0,0,0,课堂练习,0.430.15(),0.0645,4,添0,填一填。,8.5的小数点先向右移动两位，再向左移动三位，结果是（）。,0.85,你能给下面的积点上小数点吗？,0,0,0,.,.,.,0,0,根据1283384，直接写得数。12.80.3 1.280.30.1280.3 0.1280.03,3.84,0.384,0.0384,0.00384,口算。2.50.4 0.10.3 0.1220 1.250.8 3.20.2 1.50.4105.6 0.20.3,1,0.03,2.4,1,0.64,0.6,56,0.06,不计算，说出下面各题的积有几位小数。2.35.4 0.250.37 8.10.04 0.092.004,2位,4位,3位,5位,计算下面各题，并用计算器验算。0.270.15 0.0380.320.0491.42 0.140.320.183.2 0.030.84,0.0405,0.01216,0.06958,0.0448,0.576,0.0252,用竖式计算下面各题。0.742.03 0.0251.38,2,2.0 30.7 4,2,3,1.3 80.0 2 5,0,0,0,=1.5022,=0.0345,2,0,5,1,1,8,2,1,1,4,9,6,6,7,2,4,5,0,火眼金睛辨对错。,改正：,0.018,改正：,633.6,改正：,0.042,一块长方形铝板，长0.84米，宽0.6米；一块正方形铝板，边长0.7米。哪一块铝板的面积大一些?大多少平方米?,答：长方形铝板的面积大一些,大0.014平方米。,0.840.6,长方形铝板：,正方形铝板：,0.70.7,0.5040.49=0.014（平方米）,=0.504（平方米）,=0.49（平方米）,这节课你们都学会了哪些知识？,课堂小结,