题目内容
解方程(或比例)
①3x+16×3=102
②
=![数学公式](http://thumb.1010pic.com/pic5/latex/86472.png)
③2.4x-
x=6
④
:x=
:
.
解:①3x+16×3=102,
3x+48=102,
3x+48-48=102-48,
3x=54,
3x÷3=54÷3,
x=18;
②
=
,
0.6x=2×0.15,
0.6x=0.3,
0.6x÷0.6=0.3÷0.6,
x=0.5;
③2.4x-
x=6,
2.4x-0.6x=6,
(2.4-0.6)x=6,
1.8x=6,
1.8x÷1.8=6÷1.8,
x=
;
④
:x=
:
,
x=
×
,
x=
,
x×6=
×6,
x=
.
分析:①先求出16×3=48,原式变为3x+48=102,根据等式的性质,两边同减去48,再同除以3即可;
②先根据比例的性质改写成0.6x=2×0.15,再根据等式的性质,两边同除以0.6即可;
③先把
化成小数是0.6,运用乘法分配律的逆运算,把原式变为(2.4-0.6)x=6,即1.8x=6,再根据等式的性质,两边同除以1.8即可;
④先根据比例的性质改写成
x=
×
,再根据等式的性质,两边同乘6即可.
点评:此题考查了根据等式的性质解方程,即方程两边同加、同减、同乘或同除以某数(0除外),方程的左右两边仍相等;注意“=”号上下要对齐.
3x+48=102,
3x+48-48=102-48,
3x=54,
3x÷3=54÷3,
x=18;
②
![](http://thumb.1010pic.com/pic5/latex/223.png)
![](http://thumb.1010pic.com/pic5/latex/86472.png)
0.6x=2×0.15,
0.6x=0.3,
0.6x÷0.6=0.3÷0.6,
x=0.5;
③2.4x-
![](http://thumb.1010pic.com/pic5/latex/14.png)
2.4x-0.6x=6,
(2.4-0.6)x=6,
1.8x=6,
1.8x÷1.8=6÷1.8,
x=
![](http://thumb.1010pic.com/pic5/latex/395.png)
④
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/7.png)
![](http://thumb.1010pic.com/pic5/latex/597.png)
![](http://thumb.1010pic.com/pic5/latex/7.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/597.png)
![](http://thumb.1010pic.com/pic5/latex/7.png)
![](http://thumb.1010pic.com/pic5/latex/593.png)
![](http://thumb.1010pic.com/pic5/latex/7.png)
![](http://thumb.1010pic.com/pic5/latex/593.png)
x=
![](http://thumb.1010pic.com/pic5/latex/2235.png)
分析:①先求出16×3=48,原式变为3x+48=102,根据等式的性质,两边同减去48,再同除以3即可;
②先根据比例的性质改写成0.6x=2×0.15,再根据等式的性质,两边同除以0.6即可;
③先把
![](http://thumb.1010pic.com/pic5/latex/14.png)
④先根据比例的性质改写成
![](http://thumb.1010pic.com/pic5/latex/7.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/597.png)
点评:此题考查了根据等式的性质解方程,即方程两边同加、同减、同乘或同除以某数(0除外),方程的左右两边仍相等;注意“=”号上下要对齐.
![](http://thumb2018.1010pic.com/images/loading.gif)
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