五年级上册数学讲义小数乘除法混合运算人教版含答案Word文件下载.docx
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小数乘除法混合运算的运算顺序与整数乘除法混合运算的顺序相同。
小数四则混合运算的顺序跟整数是一样的。
例1.口算
例2.
计算下面各题。
(1)[60-(9.5+28.9)]×
1.5
(2)(37.5-36÷
3.6)÷
2.5
例3.(海珠区单元卷)递等式计算
(1)0.75×
1.8÷
0.15
(2)3.072÷
6.4+49.7
(3)(3.2+0.56)÷
0.8(4)60.8-36÷
7.5
我爱展示
1.计算下面各题。
(1)2.6+1.4×
1.5-1.5
(2)30.8÷
[14-(9.85+1.07)]
(3)2.6+24×
(1.4-1.05)(4)28-(3.4+1.25×
2.4)
知识点讲解2小数乘除法之乘法交换律、结合律巧算
若为同级,则用“凑整”,一般运用到乘法交换律,或用“去添括号”。
例1.计算下面各题
(1)1.25×
0.4×
8×
2.5
(2)80×
1.25×
0.4
(3)64×
0.25×
0.5(4)1.25×
9.98×
2.5×
320
例2.计算下题
144÷
100
例3.3.9÷
(1.3÷
1.5)
例4.3.6×
(1.6÷
1.2)
1.用简便方法计算下题
(1)0.125×
64×
0.5
(2)0.25×
4×
0.8
(3)3.6×
(1.9÷
知识点讲解3小数四则运算之乘法分配律巧算
例1.填空题
0.7×
1.2○1.2×
0.7
(0.8×
0.5)×
0.4○0.8×
(0.5×
0.4)
(2.4+3.6)×
0.5○2.4×
0.5+3.6×
0.5
例2.用简便方法计算下列各题
(1)6.5×
3.3+6.5×
6.7
(2)12.5×
12.3-1.25×
23
(3)8.5×
1.7+0.85×
83(4)99.9×
116-99.9×
16
(5)1.8+128×
1.8-29×
1.8
例3.[单选题](海珠区单元卷)计算2.6×
101-2.6,下面的算法比较简便的是()。
A.B.C.按照运算顺序列竖式计算
1.下面各题计算得对吗?
把不对的改正过来
(1)2.4×
3.9-3.8
=2.4×
0.1改正
=0.24()
(2)0.26×
0.85+7.8
=0.221+7.8改正
=8.021()
2.填空题
2.1=○0.4
(12.3×
4)×
2.5=○(×
2.5)
(8+0.4)×
25=×
25+×
25
9.8×
124=(-)×
124=×
-×
3.简便计算
(1)0.56×
9.9
(2)7.3×
1.2+12×
0.27
(3)327×
2.8+17.8×
28(4)4.3×
1.3+8.4×
1.3-2.7×
1.3
我当小老师
(1)今天学了小数乘除的哪些运算定律?
(2)小数四则运算规则是什么?
限时考场模拟
1.
填空题
(1)3.12×
0.5=□×
□12.5×
8.7×
0.8=(□×
□)×
□
(2)4.1×
1.5+5.9×
1.5=(□+□)×
(3)3.56×
3+7×
3.56可以用()律进行简算,0.25×
9.5×
8可以用()
律进行简算。
2.[单选题]2.4×
0.56+7.6×
0.56=(2.4+7.6)×
0.56运用了()。
A.乘法的交换律B.乘法的结合律C.乘法的分配律3.计算下列各题,尽量选用简便算法
4.(越秀区单元卷)
(1)3.4×
0.9+6.6×
0.9
(2)3.21+3.21×
99
课后作业
1.计算下面各题,能简算的要简算。
(1)120-3.6×
4÷
1.8+35
(2)5.4÷
[2.6×
(3.7-2.9)+0.62]
2.
(1)0.125×
64
(2)0.68×
101
3.
(1)3.26×
6.2-3.26×
1.2
(2)55.6×
99+55.6
4.(越秀区单元卷)5.72-(0.24×
3+1.6)
(1)把运算定律整理到笔记本上
(2)进行错题整理,并重新复习一下例题
1.
(1)0.63;
(2)765;
(3)0.72;
(4)0.3;
(5)0.064;
(6)0.7;
2.
(1)9000;
(2)1300;
(3)4500。
知识点讲解1、小数乘除法计算例题
1.
2.
(1)32.4;
(2)11
解析:
1.5
=(60-38.4)×
=21.6×
=32.4
(2)(37.5-36÷
=(37.5-10)÷
=27.5÷
=1.1
3.
(1)63.7;
(2)42;
(3)37;
(4)1.246
0.15=0.75÷
0.15×
1.8=5×
1.8=9
(2)3.072÷
6.4+49.7=0.48+49.7=50.18
(3)(3.2+0.56)÷
0.8=3.2÷
0.8+0.56÷
0.8=4+0.7=4.7
(4)60.8-36÷
7.5=60.8-4.8=56
1.
(1)3.2;
(2)10;
(3)11;
(4)21.6
1.5-1.5
=2.6+2.1-1.5
=3.2
(2)30.8÷
=30.8÷
[14-10.92]
3.08
=10
(1.4-1.05)
=2.6+24×
0.35
=2.6+8.4
=11
(4)28-(3.4+1.25×
=28-(3.4+4)
=28-7.4
=20.6
知识点讲解2小数乘除法之乘法交换律、结合律巧算例题
1.
(1)10;
(2)1000;
(3)10;
(4)9980
=10×
1
(2)80×
=100×
10
=1000
=(8×
1.25)×
(4×
0.25)×
(2×
0.5)
1×
(4)1.25×
=(1.25×
8)×
(9.98×
10)×
(2.5×
4)
99.8×
=9980
2.576
144÷
=144×
100÷
(100÷
25)
4
=576
3.4.5
3.9÷
=3.9÷
1.3×
=3×
=4.5
4.4.8
3.6×
=3.6×
1.6÷
1.2
=3.6÷
1.2×
1.6
=4.8
(2)1;
(3)5.7解析:
=0.125×
2×
=(0.125×
=1×
10×
(2)0.25×
=0.25×
(1.25×
0.8)
=1
1.9÷
1.9
=5.7
知识点讲解3小数四则运算之乘法分配律巧算例题
1.
(1)=;
(2)=;
(3)=
乘法交换律;
乘法分配律的运用2.
(1)65;
(2)125;
(3)85;
(4)9990解析:
6.7
=6.5×
(3.3+6.7)
=65
(2)12.5×
=12.5×
12.3-12.5×
2.3
(12.3-2.3)
=125
83
=8.5×
1.7+8.5×
8.3
(1.7+8.3)
=85
(4)99.9×
=99.9×
(116-16)
=9990
=1.8×
1+1.8×
128-1.8×
29
(1+128-29)
=180
3.A
1.
(1)×
;
17.26;
(2)√;
=9.36-3.8
=5.56
2.
(1)2.1;
×
;
(2)12.3;
×
4;
(3)8;
0.4;
(4)10;
0.2;
10;
124;
乘法交换律,乘法结合律和乘法分配律3.
(1)5.04;
(2)12;
(3)1400;
(4)13解析:
9.9
=0.56×
(10-0.1)
10-0.56×
=5.6-0.56
=5.04
(2)7.3×
=1.2×
7.3+1.2×
2.7
(7.3+2.7)
=12
28
=28×
32.7+28×
17.8
(32.7+17.8)
50
=1400
(4)4.3×
=1.3×
(4.3+8.4-2.7)
=13
1.
(1)0.5,3.12;
12.5,0.8,8.7
(2)4.1,5.9,1.5;
(3)乘法分配;
乘法结合
2.C
3.
(1)2.16;
(2)4.5;
(3)9;
(4)8.405;
(5)277.2;
(6)763;
4.
(1)9;
(2)321
(1)3.4×
0.9
=0.9×
(3.4+6.6)
=9
(2)3.21+3.21×
=3.21×
(99+1)
=321
1.
(1)147;
(2)2;
1.8+35
=120-3.6÷
1.8×
4+35
=120-2×
=120-8+35
=112+35
=147
(2)5.4÷
=5.4÷
0.8+0.62]
[2.08+0.62]
=2
2.
(1)8;
(2)68.68解析:
64
=0.125×
8
=8
(2)0.68×
=0.68×
(100+1)
100+0.68×
=68+0.68
=68.683.
(1)16.3;
(2)5560
(1)3.26×
=3.26×
(6.2-1.2)
5
=16.3
(2)55.6×
=55.6×
99+55.6×
=5560
4.3.4
5.72-(0.24×
=5.72-0.72-1.6
=3.4