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a) 35 : 5 và (35 x 4) : (5 x 4)
35:5= 7
(35 x 4) : (5 x 4) = 140 : 20 =7
=> 35 : 5 = (35 x 4) : (5 x 4)
b) 105 : 15 và (105 : 5) : (15 : 5)
105:15 =7
(105 : 5) : (15 : 5)= 7 : 3= 2 (dư 1)
=>105 : 15 > (105 : 5) : (15 : 5)
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1260:(x:35)=105
x:35=1260:105
x:35=12
x=12x35
x=420
Vậy x=420.
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51/60 x 12/17 : 3/10= 51/60 x 12/17 x 10/3 = 6120/3060 = 2
5/12 : 7/4 - 25/18 : 35/6 = 5/12 x 4/7 - 25/18 x 6/35 = 5/21 - 5/21 = 0
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(X + 3054) : 5 = 1230
X + 3054 = 1230 x 5
X + 3054 = 6150
X = 6150 - 3054
X = 3096
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x3 + x2 + x4 + x = 1230
\(\Rightarrow\)x10 = 1230
\(\Rightarrow\)x = 1230 : 10
\(\Rightarrow\)x = 123
vậy x = 123
x * 3 + x * 2 + x * 4 + x = 1230
x * 3 + x* 2 + x * 4 + x * 1 =1230
x* ( 3 + 2 + 4 + 1 ) = 1230
x * 10 = 1230
x = 1230 : 10
x = 123
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a, 1260:{x:35}=105
x:35 = 1260 : 105
x:35 = 12
x = 12*35
x = 420
b, 6885:{135:x}=153
135:x = 6885:153
135:x = 45
x = 135 : 45
x = 3
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
Tính nhanh:
\(10+20+30+40+50+60+70+80+90+100\)
\(=\left(10+90\right)+\left(20+80\right)+\left(30+70\right)+\left(60+40\right)+50+100\)
\(=100+100+100+100+150\)
\(=550\)
Tính:
40 + 1 230 = 1 270
1 230 + 40 = 1 270
67 478 + 9 076 = 76 554
9 076 + 67 478 = 76 554
Tính nhanh:
10 + 20 + 30 + 40 + 50 + 60 + 70 + 80 + 90 + 100
= (10 + 90) + (20 + 80) + (30 + 70) + (40 + 60) + (100 + 50)
= 100 + 100 + 100 + 100 + 150
= 100 \(\times\) 4 + 150
= 400 + 150
= 550
`1230:(x:35)=105`
`=>x:35=1230:105`
`=>x:35=82/7`
`=>x=82/7×35`
`=>x=410`
=> x:35=1230/105
=>x=1230/105.35=410