题目内容
计算.
(1)1.25×17.6+36.1÷0.8+2.63×12.5
(2)(78.6-0.786×25十75%×21.4)÷15×2011.
解:(1)1.25×17.6+36.1÷0.8+2.63×12.5,
=1.25×17.6+36.1÷
+26.3×1.25,
=1.25×17.6+36.1×1.25+26.3×1.25,
=(17.6+36.1+26.3)×12.5,
=80×1.25,
=100;
(2)(78.6-0.786×25+75%×21.4)÷15×2011,
=(78.6-0.786×25+
×21.4)÷15×(2000+11),
=(78.6-0.786×100×
+
×21.4)÷15×(2000+11),
=(78.6-78.6×
+
×21.4)÷15×(2000+11),
=[78.6×(1-
)+
×21.4]÷15×(2000+11),
=[78.6×
+
×21.4]÷15×(2000+11),
=[(78.6+21.4)×
]÷15×(2000+11),
=[100×
]÷15×(2000+11),
=75÷15×(2000+11)
=5×(2000+11),
=10000+55,
=10055.
分析:(1)根据数字特点,把原式变为1.25×17.6+36.1÷
+26.3×1.25,即1.25×17.6+36.1×1.25+26.3×1.25,然后运用乘法分配律简.
(2)根据数字特点,可将算式改写成(78.6-0.786×25+
×21.4)÷15×(2000+11),再把25写成100×
,运用乘法分配律进行计算.
点评:此题主要考查是的小数的四则混合运算和简便运算,这两题在计算时,充分利用了乘法分配律.
=1.25×17.6+36.1÷
![](http://thumb.1010pic.com/pic5/latex/602.png)
=1.25×17.6+36.1×1.25+26.3×1.25,
=(17.6+36.1+26.3)×12.5,
=80×1.25,
=100;
(2)(78.6-0.786×25+75%×21.4)÷15×2011,
=(78.6-0.786×25+
![](http://thumb.1010pic.com/pic5/latex/365.png)
=(78.6-0.786×100×
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
=(78.6-78.6×
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
=[78.6×(1-
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
=[78.6×
![](http://thumb.1010pic.com/pic5/latex/365.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
=[(78.6+21.4)×
![](http://thumb.1010pic.com/pic5/latex/365.png)
=[100×
![](http://thumb.1010pic.com/pic5/latex/365.png)
=75÷15×(2000+11)
=5×(2000+11),
=10000+55,
=10055.
分析:(1)根据数字特点,把原式变为1.25×17.6+36.1÷
![](http://thumb.1010pic.com/pic5/latex/602.png)
(2)根据数字特点,可将算式改写成(78.6-0.786×25+
![](http://thumb.1010pic.com/pic5/latex/365.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
点评:此题主要考查是的小数的四则混合运算和简便运算,这两题在计算时,充分利用了乘法分配律.
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目