题目内容
简算
2.04×92+20.4×0.8
100×![数学公式](http://thumb.1010pic.com/pic5/latex/178471.png)
1.25×32×2.5
.
解:(1)2.04×92+20.4×0.8,
=20.4×9.2+20.4×0.8,
=20.4×(9.2+0.8),
=20.4×10,
=204;
(2)100×
,
=(99+1)×
,
=99×
+1×
,
=7+
,
=7
;
(3)1.25×32×2.5,
=1.25×8×4×2.5,
=(1.25×8)×(4×2.5),
=10×10,
=100;
(4)
÷
+
÷
,
=(
+
)÷
,
=1÷
,
=
.
分析:(1)根据数字特点,先把原式变为20.4×9.2+20.4×0.8,运用乘法分配律简算;
(2)把100看作99+1,运用乘法分配律简算;
(3)把32看作8×4,运用乘法结合律简算;
(4)运用除法的性质简算,然后根据倒数的概念,写出答案.或先把除法改为乘法,运用乘法分配律简算.
点评:完成此题,应注意审题,运用合适的简便方法计算.
=20.4×9.2+20.4×0.8,
=20.4×(9.2+0.8),
=20.4×10,
=204;
(2)100×
![](http://thumb.1010pic.com/pic5/latex/178471.png)
=(99+1)×
![](http://thumb.1010pic.com/pic5/latex/178471.png)
=99×
![](http://thumb.1010pic.com/pic5/latex/178471.png)
![](http://thumb.1010pic.com/pic5/latex/178471.png)
=7+
![](http://thumb.1010pic.com/pic5/latex/178471.png)
=7
![](http://thumb.1010pic.com/pic5/latex/178471.png)
(3)1.25×32×2.5,
=1.25×8×4×2.5,
=(1.25×8)×(4×2.5),
=10×10,
=100;
(4)
![](http://thumb.1010pic.com/pic5/latex/1154.png)
![](http://thumb.1010pic.com/pic5/latex/12891.png)
![](http://thumb.1010pic.com/pic5/latex/4458.png)
![](http://thumb.1010pic.com/pic5/latex/12891.png)
=(
![](http://thumb.1010pic.com/pic5/latex/1154.png)
![](http://thumb.1010pic.com/pic5/latex/4458.png)
![](http://thumb.1010pic.com/pic5/latex/12891.png)
=1÷
![](http://thumb.1010pic.com/pic5/latex/12891.png)
=
![](http://thumb.1010pic.com/pic5/latex/1286.png)
分析:(1)根据数字特点,先把原式变为20.4×9.2+20.4×0.8,运用乘法分配律简算;
(2)把100看作99+1,运用乘法分配律简算;
(3)把32看作8×4,运用乘法结合律简算;
(4)运用除法的性质简算,然后根据倒数的概念,写出答案.或先把除法改为乘法,运用乘法分配律简算.
点评:完成此题,应注意审题,运用合适的简便方法计算.
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目
计算下列各题,能简算的要简算.
2.56÷0.04÷0.5 | 1.92÷0.12-2.7 | 37.3-1.5÷0.24 | 7.52×0.65÷0.752. |