题目内容
下列各题怎样简便就怎样计算
(1)![数学公式](http://thumb.1010pic.com/pic5/latex/408354.png)
(2)![数学公式](http://thumb.1010pic.com/pic5/latex/408355.png)
(3)2012×20.11-201.2×201
(4)
.
解:
+(5+7
×3
)×
,
=
+(5+26)×
,
=
+31×
,
=3
;
(2)1.75×0.24+0.76÷
,
=1.75×0.24+0.76×1.75,
=1.75×(0.24+0.76),
=1.75×1,
=1.75;
(3)2012×20.11-201.2×201,
=201.2×201.1-201.2×201,
=201.2×(201.1-201),
=201.2×0.1,
=20.12;
(4)1-
-
-![](http://thumb.1010pic.com/pic5/latex/28602.png)
,
=1-(
+
+
+
),
=1-
,
=![](http://thumb.1010pic.com/pic5/latex/408358.png)
分析:(1)按则运算的顺序,先算小括号里的乘,再算小括号里的加,然后算括号外面的乘,最后算括号外面的加;
(2)把0.76÷
变成0.76×1.75,利用乘法的分配律变成1.75×(0.24+0.76)计算简便;
(3)把2012×20.11变成201.2×201.1,利用乘法的分配律变,201.2×(201.1-201)计算简便;
(4)把原算是变成1-(
+
+
+
)计算简便.
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算.
![](http://thumb.1010pic.com/pic5/latex/36.png)
![](http://thumb.1010pic.com/pic5/latex/602.png)
![](http://thumb.1010pic.com/pic5/latex/8.png)
![](http://thumb.1010pic.com/pic5/latex/318303.png)
=
![](http://thumb.1010pic.com/pic5/latex/36.png)
![](http://thumb.1010pic.com/pic5/latex/318303.png)
=
![](http://thumb.1010pic.com/pic5/latex/36.png)
![](http://thumb.1010pic.com/pic5/latex/318303.png)
=3
![](http://thumb.1010pic.com/pic5/latex/36.png)
(2)1.75×0.24+0.76÷
![](http://thumb.1010pic.com/pic5/latex/4458.png)
=1.75×0.24+0.76×1.75,
=1.75×(0.24+0.76),
=1.75×1,
=1.75;
(3)2012×20.11-201.2×201,
=201.2×201.1-201.2×201,
=201.2×(201.1-201),
=201.2×0.1,
=20.12;
(4)1-
![](http://thumb.1010pic.com/pic5/latex/63.png)
![](http://thumb.1010pic.com/pic5/latex/851.png)
![](http://thumb.1010pic.com/pic5/latex/28602.png)
![](http://thumb.1010pic.com/pic5/latex/408357.png)
=1-(
![](http://thumb.1010pic.com/pic5/latex/63.png)
![](http://thumb.1010pic.com/pic5/latex/851.png)
![](http://thumb.1010pic.com/pic5/latex/28602.png)
![](http://thumb.1010pic.com/pic5/latex/15503.png)
=1-
![](http://thumb.1010pic.com/pic5/latex/71604.png)
=
![](http://thumb.1010pic.com/pic5/latex/408358.png)
分析:(1)按则运算的顺序,先算小括号里的乘,再算小括号里的加,然后算括号外面的乘,最后算括号外面的加;
(2)把0.76÷
![](http://thumb.1010pic.com/pic5/latex/4458.png)
(3)把2012×20.11变成201.2×201.1,利用乘法的分配律变,201.2×(201.1-201)计算简便;
(4)把原算是变成1-(
![](http://thumb.1010pic.com/pic5/latex/63.png)
![](http://thumb.1010pic.com/pic5/latex/851.png)
![](http://thumb.1010pic.com/pic5/latex/28602.png)
![](http://thumb.1010pic.com/pic5/latex/15503.png)
点评:考查了运算定律与简便运算,四则混合运算.注意运算顺序和运算法则,灵活运用所学的运算律简便计算.
![](http://thumb2018.1010pic.com/images/loading.gif)
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