(2009•翠屏区)解比例或方程.
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(2009•翠屏区)解比例或方程.
0.8x:1.2=3:0.9
5×70%+0.4x=9.1
0.8x:1.2=3:0.9
5×70%+0.4x=9.1
3 |
4 |
(1)0.8x:1.2=3:0.9,
0.8x×0.9=1.2×3,
0.72x=3.6,
0.72x÷0.72=3.6÷0.72,
x=5;
(2)5×70%+0.4x=9.1,
3.5+0.4x=9.1,
3.5+0.4x-3.5=9.1-3.5,
0.4x=5.6,
0.4x÷0.4=5.6÷0.4,
x=14;
(3)
3
4x-
2
5x=
7
10,
7
20x=
7
10,
7
20x÷
7
20=
7
10÷
7
20,
x=2;
(4)
3
7:
1
3=x:
7
12,
1
3x=
3
7×
7
12,
1
3x÷
1
3=
3
7×
7
12÷
1
3,
x=
3
7×
7
12×3,
x=
3
4.
0.8x×0.9=1.2×3,
0.72x=3.6,
0.72x÷0.72=3.6÷0.72,
x=5;
(2)5×70%+0.4x=9.1,
3.5+0.4x=9.1,
3.5+0.4x-3.5=9.1-3.5,
0.4x=5.6,
0.4x÷0.4=5.6÷0.4,
x=14;
(3)
3
4x-
2
5x=
7
10,
7
20x=
7
10,
7
20x÷
7
20=
7
10÷
7
20,
x=2;
(4)
3
7:
1
3=x:
7
12,
1
3x=
3
7×
7
12,
1
3x÷
1
3=
3
7×
7
12÷
1
3,
x=
3
7×
7
12×3,
x=
3
4.