《小学数学五级上册小数乘法的简便运算课件.pptx
文本预览下载声明
Evaluation only.
Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.
Copyright 2004-2011 Aspose Pty Ltd.
看谁算得快
0.32×100
24＋0.24
15－0.15
0.4×0.5
1.25×8
2.5×4
0.24×5
0.6×0.1
= 32
= 24.24
= 14.85
= 0.2
= 10
= 10
= 1.2
= 0.06
0.5×0.2= 50×0.2= 500×0.2=
0.1
10
100
2.5×0.4
= 1
0.25×40
= 10
1.25×0.8
= 1
1.25×80
= 100
Evaluation only.
Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.
Copyright 2004-2011 Aspose Pty Ltd.
2、在括号里填上适当的数。
(1)0.32=4×( ) (2)1.02=1+( )
(3)0.99=1-( ) (4)9.8=( )-( )
0.08
10
0.01
0.02
0.2
Evaluation only.
Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.
Copyright 2004-2011 Aspose Pty Ltd.
看谁算得巧
(23×4)×15
25×73×4
102×32
= 25×4×73
= 100×73
= 7300
= 23×(4×15)
= 23×60
= 1380
= (100+2)×32
= 100×32+2×32
= 3200+64
= 3264
Evaluation only.
Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.
Copyright 2004-2011 Aspose Pty Ltd.
3、思考：乘法有哪些运算定律？
怎样用字母式子表示？
乘法交换律：
a×b=b×a
乘法结合律：
(a×b) ×c=a× (b×c)
乘法分配律：
(a+b) ×c=a×c+b×c
Evaluation only.
Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.
Copyright 2004-2011 Aspose Pty Ltd.
观察下面每组的两个算式，它们有什么关系？
=
=
=
整数乘法的交换律、结合律和分配律，对于小数乘法同样适用。
Evaluation only.
Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.
Copyright 2004-2011 Aspose Pty Ltd.
＝1×4.78
＝4.78
0.25×4.78×4
0.65×201
＝130＋0.65
＝130.65
＝0.25×4×4.78
＝0.65×（200＋1）
＝0.65×200＋0.65
例8
根据乘法交换律
乘法分配律
Evaluation only.
Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.
Copyright 2004-2011 Aspose Pty Ltd.
小数简便计算计算应注意的问题：
一审：
审清题目。
二看：
观察数字特征，选择合理的运算定律。
三算：
认真计算。
四查：
查运算顺序；查数字；查每一步的计算。
Evaluation only.
Created with Aspose.Slides for .NET 3.5 Client Profile 5.2.0.0.
Copyright 2004-2011 Aspose Pty Ltd.
4.2×1.69＝ ×
2.5×0.77×0.4＝（ × ）×
6.1×3.6+3.9×3.6＝（ ＋ ）×
1.69
4.2
2.5
0.4
0.77
6.1
3.9
3.6
Evaluation only.
Cre
显示全部