解题思路:(1)4x+0.4x=70.4,根据乘法分配律化简为:4.4x=70.4,两边同时除以4.4即可;
(2)3x+90%×4=9,把百分数化成小数,将方程化简为,3x+3.6=9,两边同时减3.6,然后两边同时除以3即可;
(3)x-40%x=42,把百分数化成小数,将方程化简为,0.6x=42,两边同时除以0.6即可;
(4)120%x-x=24,把百分数化成小数,将方程化简为,0.2x=24,两边同时除以0.2即可;
(5)1-20%x=[1/4],把百分数化成小数,将方程化简为,0.2x=1-0.25,两边同时除以0.2即可;
(6)[1/4]+20%x=1.把百分数化成小数,将方程化简为,0.25+0.2x=1,两边同时减0.25,再把两边同时除以0.2即可.
(1)4x+0.4x=70.4,
4.4x=70.4,
4.4x÷4.4=70.4÷4.4,
x=16;
(2)3x+90%×4=9,
3x+3.6=9,
3x+3.6-3.6=9-3.6,
3x=5.4;
3÷3x=5.4÷3,
x=1.8;
(3)x-40%x=42,
0.6x=42,
0.6x÷0.6=42÷0.6,
x=70;
(4)120%x-x=24,
0.2x=24,
0.2x÷0.2=24÷0.2,
x=120;
(5)1-20%x=[1/4],
0.2x=1-0.25,
0.2x=0.75,
0.2x÷0.2=0.75÷0.2,
x=0.375;
(6)[1/4]+20%x=1.
0.25+0.2x=1,
0.25+0.2x-0.25=1-0.25;
0.2x=0.75,
0.2x÷0.2=0.75÷0.2,
x=3.75.
点评:
本题考点: 方程的解和解方程.
考点点评: 此题考查的目的是理解方程的意义,掌握利用等式的性质解方程的方法步骤.