小数加减混合运算青岛版四年级数学下册昌乐育才双语学校 李永秀Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.1.大家都有朋友，有新朋友和老朋友，在数学的学 习过程中，我们也要学会找朋友。79+145+21 25+97+3 在每个算式中找到一对好朋友，并说明为什么？2.整数加法的运算定律。a+b=b+a (a+b)+c=a+(b+c)3.找朋友：看哪两个数相加和是整数。8.8 0.36.9 1.219.7 2.11.03 0.972.99 2.01Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.本节课我们主要来学习小数加减法混 合运算，同学们结合具体的实例理解 并掌握小数加减法的计算方法，能够 解决相关的实际问题。Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.出生时 满月时 白天时身 高 0.78米 0.81米比满月时多 0.16克隆牛“蓓蓓”身高情况记录Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.“蓓蓓”出生时的体长是多少？“蓓蓓”百天时的身高比出生时增加了 多少米？我们的问题：Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.可以有几种解法？0.98-0.22-0.10.76-0.10.66（米）0.98-0.22-0.1 0.98-（0.22+0.1） 0.98-0.32 0.66 （米）Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.2.86+1.45+0.14=2.86+0.14+1.45=3+1.45=4.454.8+8.63+5.2+0.37=(4.8+5.2)+(8.63+0.37) =10+9 =19你会计算吗？Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.原来学过的交换律、结合律、在小数中仍然适用，可以使计算简便 。你有什么新发现Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.下列每组算式两边的结果相等吗？(1) 0.4+0.80.8+.04(2) (2.6+5.3)+1.72.6+(5.3+1.7)=Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.3.24根据运算定律填空。8.03-2.16-3.84=8.03-( + )=2.163.845.93+(0.19+2.81)5.93+0.19+2.811.76+0.195+3.24(1.76+ )+0.195=Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.试剑石（二）13.7+17.5-9.621.2-9.611.62-1.75+0.250.250.250.5Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.你能完成吗： 1.76+0.195+3.242.35+1.713+0.287+7.65=(1.76+3.24)+0.195 =5+0.195 =5.195=(2.35+7.65)+(1.713+0.287) =10+2 =12Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.一堆煤12.4吨，连续三个星期分别用 去2.8吨、3.4吨和3.8吨，还剩多少 吨煤？ Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.小华的纸飞机在空中飞了15.6秒，比小玲 的纸飞机多飞了2.8秒，小冬的纸飞机比 小玲少飞2.8秒，小冬的纸飞机在空中飞 了多少秒？Evaluation only.Evaluation only. Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0. Copyright 2004-2011 Aspose Pty Ltd.Copyright 2004-2011 Aspose Pty Ltd.