题目内容
脱式计算,写出主要计算过程,能用简便算法的要用简便算法. ①12× ![]() ![]() | ②(![]() ![]() | ③![]() ![]() |
④3.6-2.8+6.4-7.2 | ⑤2-![]() ![]() ![]() | ⑥(![]() ![]() ![]() |
解:①12×
÷![](http://thumb.1010pic.com/pic5/latex/365.png)
=12×
×
,
=6;
②(
+
)×36
=
×36+
×36,
=9+8,
=17;
③
+
×13
=
+7,
=7
;
④3.6-2.8+6.4-7.2
=3.6+6.4-(2.8+7.2),
=10-10,
=0;
⑤2-
÷
-![](http://thumb.1010pic.com/pic5/latex/7.png)
=2-
-
,
=2-(
+
),
=2-1,
=1;
⑥(
+
)÷(1-
)
=
÷
,
=
.
分析:①③⑥根据四则混合运算的运算顺序计算即可:先算乘除,现算加减,有括号的要先算括号里面的;
②可根据乘法分配律计算;
⑤可根据一个数减两个数,等于用这个数减去两个数的差的减法性质计算.
④可根据加法交换律及一个数减两个数,等于用这个数减去两个数的差的减法性质计算.
点评:完成此类题目要细心分析式中数据的特点及内在联系,然后运用合适的方法进行计算.
![](http://thumb.1010pic.com/pic5/latex/597.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
=12×
![](http://thumb.1010pic.com/pic5/latex/597.png)
![](http://thumb.1010pic.com/pic5/latex/304.png)
=6;
②(
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/3982.png)
=
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/3982.png)
=9+8,
=17;
③
![](http://thumb.1010pic.com/pic5/latex/14169.png)
![](http://thumb.1010pic.com/pic5/latex/28406.png)
=
![](http://thumb.1010pic.com/pic5/latex/14169.png)
=7
![](http://thumb.1010pic.com/pic5/latex/14169.png)
④3.6-2.8+6.4-7.2
=3.6+6.4-(2.8+7.2),
=10-10,
=0;
⑤2-
![](http://thumb.1010pic.com/pic5/latex/168.png)
![](http://thumb.1010pic.com/pic5/latex/602.png)
![](http://thumb.1010pic.com/pic5/latex/7.png)
=2-
![](http://thumb.1010pic.com/pic5/latex/155.png)
![](http://thumb.1010pic.com/pic5/latex/7.png)
=2-(
![](http://thumb.1010pic.com/pic5/latex/155.png)
![](http://thumb.1010pic.com/pic5/latex/7.png)
=2-1,
=1;
⑥(
![](http://thumb.1010pic.com/pic5/latex/8.png)
![](http://thumb.1010pic.com/pic5/latex/13.png)
![](http://thumb.1010pic.com/pic5/latex/597.png)
=
![](http://thumb.1010pic.com/pic5/latex/155.png)
![](http://thumb.1010pic.com/pic5/latex/5192.png)
=
![](http://thumb.1010pic.com/pic5/latex/304.png)
分析:①③⑥根据四则混合运算的运算顺序计算即可:先算乘除,现算加减,有括号的要先算括号里面的;
②可根据乘法分配律计算;
⑤可根据一个数减两个数,等于用这个数减去两个数的差的减法性质计算.
④可根据加法交换律及一个数减两个数,等于用这个数减去两个数的差的减法性质计算.
点评:完成此类题目要细心分析式中数据的特点及内在联系,然后运用合适的方法进行计算.
![](http://thumb2018.1010pic.com/images/loading.gif)
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