题目内容
解方程.
(1)37.5+20%X=69.5
(2)![数学公式](http://thumb.1010pic.com/pic5/latex/203546.png)
(3)
÷χ=
.
解:(1)37.5+20%X=69.5,
37.5+0.2X=69.5,
37.5+0.2X-37.5=69.5-37.5,
0.2X=32,
0.2X÷0.2=32÷0.2,
x=160;
(2)120+
x=168,
120+0.8x=168,
120+0.8x-120=168-120,
0.8x=48,
0.8x÷0.8=48÷0.8,
x=60;
(3)
÷x=
,
÷x×x=
×x,
x=
,
x×
=
×
,
x=
.
分析:(1)原式变为37.5+0.2X=69.5,根据等式的性质,两边同减去37.5,再同除以0.2即可;
(2)原式变为120+0.8x=168,根据等式的性质,两边同减去120,再同除以0.8即可;
(3)根据等式的性质,两边同乘x,得
x=
,两边再同乘
即可.
点评:此题考查了根据等式的性质解方程,即等式两边同加、同减、同乘或同除以一个数(0除外),等式的左右两边仍相等;注意“=”上下要对齐.
37.5+0.2X=69.5,
37.5+0.2X-37.5=69.5-37.5,
0.2X=32,
0.2X÷0.2=32÷0.2,
x=160;
(2)120+
![](http://thumb.1010pic.com/pic5/latex/602.png)
120+0.8x=168,
120+0.8x-120=168-120,
0.8x=48,
0.8x÷0.8=48÷0.8,
x=60;
(3)
![](http://thumb.1010pic.com/pic5/latex/14.png)
![](http://thumb.1010pic.com/pic5/latex/9777.png)
![](http://thumb.1010pic.com/pic5/latex/14.png)
![](http://thumb.1010pic.com/pic5/latex/9777.png)
![](http://thumb.1010pic.com/pic5/latex/9777.png)
![](http://thumb.1010pic.com/pic5/latex/14.png)
![](http://thumb.1010pic.com/pic5/latex/9777.png)
![](http://thumb.1010pic.com/pic5/latex/7580.png)
![](http://thumb.1010pic.com/pic5/latex/14.png)
![](http://thumb.1010pic.com/pic5/latex/7580.png)
x=
![](http://thumb.1010pic.com/pic5/latex/3724.png)
分析:(1)原式变为37.5+0.2X=69.5,根据等式的性质,两边同减去37.5,再同除以0.2即可;
(2)原式变为120+0.8x=168,根据等式的性质,两边同减去120,再同除以0.8即可;
(3)根据等式的性质,两边同乘x,得
![](http://thumb.1010pic.com/pic5/latex/9777.png)
![](http://thumb.1010pic.com/pic5/latex/14.png)
![](http://thumb.1010pic.com/pic5/latex/7580.png)
点评:此题考查了根据等式的性质解方程,即等式两边同加、同减、同乘或同除以一个数(0除外),等式的左右两边仍相等;注意“=”上下要对齐.
![](http://thumb2018.1010pic.com/images/loading.gif)
练习册系列答案
相关题目