数学问题

Question

怎样简便怎样算
2.8x2.48+2.8x1.52 1.14x8-1.14+1.14x3
= =

0.36x7.5+0.036x25 0.375x101-37.5
= =

2.5x32x1.25 6.25x1.02/1.5
= =

32.5x3.5+32.5x6.5 17.5/12.5x1.8
= =

19.44/2.7-6.49 12.5x0.7x0.8
= =

1.2x2.5+0.8x2.5 2.01x7.5-4.5x2.01
= =

解方程
3.5-5x=2 (x+3)/5=1.6 8x+2x4=31 4x+9=25 96-4x=72
7x+3=24 7+x+4x=78 13.2x+9x=33.3 (x-3)/2=7.5
2x+7.15=11.15 7x-25=0.5x27 5.6x+4x=17.28
0.72x3-0.3x=0.06 60-x=34.7+2.3

列方程并求解
1.15与一个数的2倍的和是38的一半，这个数是多少？
2.一个数与6的和除以4，商是7.5的2倍，这个数是多少？
3.一个数的5.8倍，与这个数的2.2倍的和是59.2，求这个数。
4.0.38比某数的3倍少20.2，求某数。
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Answer 1

2.8x2.48+2.8x1.52
= 2.8×（2.48+1.52）2.8×4 = 11.2

1.14x8-1.14+1.14x3
=1.14×（8- 1+3） =1.14×10=11.4

0.36x7.5+0.036x25
=0.36x7.5+0.36x2.5 = 0.36x（7.5+2.5） =0.36x10 =3.6

0.375x101-37.5
=0.375x100+0.375-37.5=0.375

2.5x32x1.25
=2.5x（4x8）x1.25=（2.5x4）x（1.25x8）=10x10 =100

6.25x1.02/1.5
=（6.25/5）x（1.02/0.3）=1.25x3.4=1.25x（2x1.7）=2.5x1.7=4.25

32.5x3.5+32.5x6.5
=32.5x（3.5+6.5）=32.5x4=30x4+2.5x4 =120+10 =130

17.5/12.5x1.8
= 2.52

19.44/2.7-6.49
=（19.44/9）/（2.7/9）-6.49=2.16/0.3 -6.49 =7.2-6.49 = 0.71

12.5x0.7x0.8
=（2.5x5）x0.7x0.8 = （2.5x0.8）x（5x0.7）= 2x3.5 =7

1.2x2.5+0.8x2.5
=2.5x（1.2+0.8）= 2.5x2 =5

2.01x7.5-4.5x2.0
= 2.0x7.5+0.01x7.5-4.5x2.0 =2.0x（7.5-4.5）+0.075=6.075

列方程：
1. 15+2X=38/2 X=2
2.（X+6）/4 = 7.5x2 X=54
3. 5.8X + 2.2X = 59.2 X=7.4
4. 0.38 = 3X - 20.2 X=6.86

Answer 2

2.8x2.48+2.8x1.52 1.14x8-1.14+1.14x3
= 2.8x(2.48+1.52) =1.14x(8-1+3)

0.36x7.5+0.036x25 0.375x101-37.5
=0.36x7.5+0.36x2.5
=0.36x(7.5+2.5) =37.5x1.01-37.5=37.5x(1.01-1)
下面的基本相同

Answer 3

2.8x2.48+2.8x1.52 1.14x8-1.14+1.14x3
= 2.8x(2.48+1.52) =1.14x(8-1+3)

解方程
3.5-5x=2 7x+3=24
-5x=2-3.5 7x=24-3

Answer 4

2.8*2.48+2.8*1.52=2.8*（2.48+1.52）=2.8*4=11.2

Answer 5

这么多，悬赏分加多点