题目内容
160÷1-0.75×60 | 246×![]() | 25×98+12![]() ![]() ![]() | 17×![]() ![]() |
解:(1)160÷1-0.75×60,
=160-45,
=115;
(2)246×
,
=2×123×
,
=2×321,
=642;
(3)25×98+12
×
+1
,
=25×(100-2)+
×
+
,
=2500-50+
+
,
=2450+
,
=2450+2.5,
=2452.5;
(4)17×
+35×
,
=(18-1)×
+(36-1)×
,
=17-
+35-
,
=17+35-(
+
),
=52-1
,
=50
.
分析:(1)先算除法和乘法,再算减法;
(2)把246改写成123×2,把分数化为
,约分计算;
(3)把98看做100-2,运用乘法分配律计算25×98,计算出分数部分,然后相加即可;
(4)把整数部分的17和35分别看作(18-1)和(36-1),运用乘法分配律和加法结合律简算.
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.
=160-45,
=115;
(2)246×
![](http://thumb.1010pic.com/pic5/latex/203512.png)
=2×123×
![](http://thumb.1010pic.com/pic5/latex/516991.png)
=2×321,
=642;
(3)25×98+12
![](http://thumb.1010pic.com/pic5/latex/13.png)
![](http://thumb.1010pic.com/pic5/latex/63.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
=25×(100-2)+
![](http://thumb.1010pic.com/pic5/latex/4620.png)
![](http://thumb.1010pic.com/pic5/latex/63.png)
![](http://thumb.1010pic.com/pic5/latex/1180.png)
=2500-50+
![](http://thumb.1010pic.com/pic5/latex/1180.png)
![](http://thumb.1010pic.com/pic5/latex/1180.png)
=2450+
![](http://thumb.1010pic.com/pic5/latex/259.png)
=2450+2.5,
=2452.5;
(4)17×
![](http://thumb.1010pic.com/pic5/latex/13365.png)
![](http://thumb.1010pic.com/pic5/latex/142177.png)
=(18-1)×
![](http://thumb.1010pic.com/pic5/latex/13365.png)
![](http://thumb.1010pic.com/pic5/latex/142177.png)
=17-
![](http://thumb.1010pic.com/pic5/latex/13365.png)
![](http://thumb.1010pic.com/pic5/latex/142177.png)
=17+35-(
![](http://thumb.1010pic.com/pic5/latex/13365.png)
![](http://thumb.1010pic.com/pic5/latex/142177.png)
=52-1
![](http://thumb.1010pic.com/pic5/latex/1261.png)
=50
![](http://thumb.1010pic.com/pic5/latex/6.png)
分析:(1)先算除法和乘法,再算减法;
(2)把246改写成123×2,把分数化为
![](http://thumb.1010pic.com/pic5/latex/516991.png)
(3)把98看做100-2,运用乘法分配律计算25×98,计算出分数部分,然后相加即可;
(4)把整数部分的17和35分别看作(18-1)和(36-1),运用乘法分配律和加法结合律简算.
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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