题目内容
下面各题怎么简便就怎么算
42×(
-
+
)
48×75%+53×
-0.75
45÷7+19×
-![数学公式](http://thumb.1010pic.com/pic5/latex/847.png)
(
-
)×(
+
)
解:(1)42×(
-
+
),
=42×
-42×
+42×
,
=35-18+9,
=26;
(2)48×75%+53×
-0.75,
=48×0.75+53×0.75-0.75,
=0.75×(48+53-1),
=0.75×100,
=75;
(3)45÷7+19×
-
,
=45×
+19×
-
×1,
=(45+19-1)×
,
=63×
,
=9;
(4)(
-
)×(
+
)
=
×![](http://thumb.1010pic.com/pic5/latex/4442.png)
=
.
分析:(1)根据乘法的分配律简算即可;
(2)先把75%和
都化成小数,再根据乘法的分配律简算;
(3)把原式变形为45×
+19×
-
×1,再根据乘法的分配律简算;
(4)同时算小括号里面的,再算括号外面的乘法.
点评:此题主要考查小数、分数四则混合运算的计算,完成本题要注意分析式中数据,运用合适的简便方法计算.
![](http://thumb.1010pic.com/pic5/latex/155.png)
![](http://thumb.1010pic.com/pic5/latex/1154.png)
![](http://thumb.1010pic.com/pic5/latex/10524.png)
=42×
![](http://thumb.1010pic.com/pic5/latex/155.png)
![](http://thumb.1010pic.com/pic5/latex/1154.png)
![](http://thumb.1010pic.com/pic5/latex/10524.png)
=35-18+9,
=26;
(2)48×75%+53×
![](http://thumb.1010pic.com/pic5/latex/365.png)
=48×0.75+53×0.75-0.75,
=0.75×(48+53-1),
=0.75×100,
=75;
(3)45÷7+19×
![](http://thumb.1010pic.com/pic5/latex/847.png)
![](http://thumb.1010pic.com/pic5/latex/847.png)
=45×
![](http://thumb.1010pic.com/pic5/latex/847.png)
![](http://thumb.1010pic.com/pic5/latex/847.png)
![](http://thumb.1010pic.com/pic5/latex/847.png)
=(45+19-1)×
![](http://thumb.1010pic.com/pic5/latex/847.png)
=63×
![](http://thumb.1010pic.com/pic5/latex/847.png)
=9;
(4)(
![](http://thumb.1010pic.com/pic5/latex/365.png)
![](http://thumb.1010pic.com/pic5/latex/1302.png)
![](http://thumb.1010pic.com/pic5/latex/3982.png)
![](http://thumb.1010pic.com/pic5/latex/8.png)
=
![](http://thumb.1010pic.com/pic5/latex/2235.png)
![](http://thumb.1010pic.com/pic5/latex/4442.png)
=
![](http://thumb.1010pic.com/pic5/latex/2520.png)
分析:(1)根据乘法的分配律简算即可;
(2)先把75%和
![](http://thumb.1010pic.com/pic5/latex/365.png)
(3)把原式变形为45×
![](http://thumb.1010pic.com/pic5/latex/847.png)
![](http://thumb.1010pic.com/pic5/latex/847.png)
![](http://thumb.1010pic.com/pic5/latex/847.png)
(4)同时算小括号里面的,再算括号外面的乘法.
点评:此题主要考查小数、分数四则混合运算的计算,完成本题要注意分析式中数据,运用合适的简便方法计算.
![](http://thumb2018.1010pic.com/images/loading.gif)
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下面各题怎么简便就怎么算:①
32.4×0.5=②
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7÷8=