题目内容
计算下面各题. 1+3+5+…+21+23 | 1+O.45÷0.9-0.25 |
![]() | ![]() |
解:(1)1+3+5+…+21+23,
=(1+23)+(3+21)+…(11+13),
=24×6,
=144;
(2)1+O.45÷0.9-0.25,
=1+0.5-0.25,
=1.5-0.25,
=1.25;
(3)4
-
4,
=5-
,
=4
;
(4)[1-(
)]
,
=[1-
]
,
=
,
=1
.
分析:(1)运用加法交换律和加法结合律,把原式化为(1+23)+(3+21)+…(11+13)即可解答,
(2)(3)(4)依据四则运算计算方法,先算第二级运算,再算第一级运算,如果只含有同一级运算,按照从左到右的顺序,有括号先算括号里面的即可解答.
点评:完成本题要注意分析式中数据,运用合适的简便方法计算,注意运算的顺序.
=(1+23)+(3+21)+…(11+13),
=24×6,
=144;
(2)1+O.45÷0.9-0.25,
=1+0.5-0.25,
=1.5-0.25,
=1.25;
(3)4
![](http://thumb.1010pic.com/pic5/latex/204651.png)
![](http://thumb.1010pic.com/pic5/latex/215382.png)
=5-
![](http://thumb.1010pic.com/pic5/latex/36.png)
=4
![](http://thumb.1010pic.com/pic5/latex/602.png)
(4)[1-(
![](http://thumb.1010pic.com/pic5/latex/36095.png)
![](http://thumb.1010pic.com/pic5/latex/163365.png)
=[1-
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/163365.png)
=
![](http://thumb.1010pic.com/pic5/latex/249563.png)
=1
![](http://thumb.1010pic.com/pic5/latex/112.png)
分析:(1)运用加法交换律和加法结合律,把原式化为(1+23)+(3+21)+…(11+13)即可解答,
(2)(3)(4)依据四则运算计算方法,先算第二级运算,再算第一级运算,如果只含有同一级运算,按照从左到右的顺序,有括号先算括号里面的即可解答.
点评:完成本题要注意分析式中数据,运用合适的简便方法计算,注意运算的顺序.
![](http://thumb2018.1010pic.com/images/loading.gif)
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