五年级上册数学课件第5单元第6课时小数乘小数二苏教.ppt

,小数乘小数（2）,五小数乘法和除法,0.13140（）0.1314.0（）0.131.40（）0.130.140（）,你能算出这些题的答案吗？列算式计算,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。,要从积的右边起数出几位点上小数点？位数不够怎么办？,探究点积中小数位不够时小数点的定位,0.280.2822456784,0.0,你能给下面各题的积点上小数点吗？,小试牛刀（教材P66练一练）,0.70.9063,1.050.0600630,0.180.30054,.,.,.,小试牛刀,10.430.15(),0.0645,4,添0,2你能给下面的积点上小数点吗？3根据1283384，直接写得数。12.80.31.280.30.1280.30.1280.03,0.36,0.0612,0.048,3.84,0.384,0.0384,0.00384,4口算。2.50.40.10.30.12201.250.83.20.21.50.4105.60.20.30.30.7,1,0.03,2.4,1,0.64,0.6,56,0.06,0.21,5列竖式计算。0.270.150.0380.320.0491.420.140.320.183.20.030.84,0.0405,0.01216,0.06958,0.0448,0.576,0.0252,归纳总结：,积中小数位不够时小数点的定位：小数乘小数可以先按照整数乘法算出积，再看乘数中一共有几位小数，有几位就从积的右边起数出几位，点上小数点，积的小数位如果不够，就在前面用0补位；积的末尾有0时，点完小数点后再去掉末尾的0。,夯实基础（教材P67练习十二）,4.根据第一栏的积，写出其他各栏的积。,0.72,7.2,7.2,0.072,7.2,5.0.670.131.020.760.045140.090.840.322.050.190.25,0.0871,0.7752,0.63,0.0756,0.656,0.0475,6.一块长方形铝板，长0.85米，宽0.6米；一块正方形铝板，边长0.72米。哪一块铝板的面积大，大多少平方米？,0.850.60.51(平方米)0.720.720.5184(平方米)0.5184平方米0.51平方米0.51840.510.0084(平方米)答：正方形铝板的面积大，大0.0084平方米。,7.一台拖拉机每小时耕地0.5公顷，1.2小时可耕地多少公顷？0.75小时可耕地多少公顷？,0.51.20.6(公顷)0.50.750.375(公顷)答：1.2小时可耕地0.6公顷，0.75小时可耕地0.375公顷。,12.直接写出得数。0.70.71.1100.240.23.50.10.20.40.65,0.49,11,0.048,0.35,0.08,3,13.计算下面各题，并用计算器验算。0.861.73.50.670.650.481.040.025,0.0756,0.0756,0.0756,