题目内容
解方程
X:0.3=0.4:0.8
x÷
=12 x÷
=
÷
.
解:(1)x:0.3=0.4:0.8,
0.8x=0.3×0.4,
0.8x÷0.8=0.12÷0.8,
x=0.15,
(2)
x÷
=12,
x×4=12,
x=12,
x×
=12×
,
x=
,
(3)x÷
=
÷
,
x:
=
:
.
x=
×
,
x×
=
×
×
,
x=
.
分析:根据比例的基本性质:两内项之积等于两外项之积,以及等式的性质即可解决问题.
点评:此题考查了利用比例的基本性质解比例和利用等式的性质解方程的方法.
0.8x=0.3×0.4,
0.8x÷0.8=0.12÷0.8,
x=0.15,
(2)
![](http://thumb.1010pic.com/pic5/latex/168.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/168.png)
![](http://thumb.1010pic.com/pic5/latex/137.png)
![](http://thumb.1010pic.com/pic5/latex/137.png)
![](http://thumb.1010pic.com/pic5/latex/597.png)
![](http://thumb.1010pic.com/pic5/latex/597.png)
x=
![](http://thumb.1010pic.com/pic5/latex/190.png)
(3)x÷
![](http://thumb.1010pic.com/pic5/latex/71643.png)
![](http://thumb.1010pic.com/pic5/latex/71644.png)
![](http://thumb.1010pic.com/pic5/latex/9169.png)
x:
![](http://thumb.1010pic.com/pic5/latex/71643.png)
![](http://thumb.1010pic.com/pic5/latex/71644.png)
![](http://thumb.1010pic.com/pic5/latex/9169.png)
![](http://thumb.1010pic.com/pic5/latex/9169.png)
![](http://thumb.1010pic.com/pic5/latex/71643.png)
![](http://thumb.1010pic.com/pic5/latex/71644.png)
![](http://thumb.1010pic.com/pic5/latex/9169.png)
![](http://thumb.1010pic.com/pic5/latex/26287.png)
![](http://thumb.1010pic.com/pic5/latex/71643.png)
![](http://thumb.1010pic.com/pic5/latex/71644.png)
![](http://thumb.1010pic.com/pic5/latex/26287.png)
x=
![](http://thumb.1010pic.com/pic5/latex/2581.png)
分析:根据比例的基本性质:两内项之积等于两外项之积,以及等式的性质即可解决问题.
点评:此题考查了利用比例的基本性质解比例和利用等式的性质解方程的方法.
![](http://thumb2018.1010pic.com/images/loading.gif)
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