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x × 2 + x × 3 + x × 4 + x = 420
X × ( 2 + 3 + 4 + 1 ) = 420
X × 10 = 420
X = 420 : 10
X = 42
\(x\times2+x\times3+x\times4+x=420\)
\(2x+3x+4x+x=420\)
\(10x=420\)
\(x=42\)
a)
160 : (4 × 8) = 160 : 32 = 5
160 : 4 : 8 = 40 : 8 = 5
Vậy 160 : (4 × 8) = 160 : 4 : 8.
96 : (3 × 8) = 96 : 24 = 4
96 : 3 : 8 = 32 : 8 = 4
Vậy 96 : (3 × 8) = 96 : 3 : 8.
105 : (5 × 7) = 105 : 35 = 3
105 : 5 : 7 = 21 : 7 = 3
Vậy 105 : (5 × 7) = 105 : 5 : 7.
Nhận xét: a : (b × c) = a : b : c
b)
270 : (9 × 6) = 270 : 9 : 6 = 30 : 6 = 5
420 : (7 × 3) = 420 : 7 : 3 = 60 : 3 = 20
144 : (2 × 8) = 144 : 2 : 8 = 72 : 8 = 9
Tìm x :
x + 1/3 = 4/5
x = 4/5 - 1/3
x = 12/15 - 5/15
x = 7/15
x - 1/2 = 2/7
x = 2/7 + 1/2
x = 4/14 + 7/14
x = 11/14
4/7 × x = 1/3
x = 1/3 : 4/7
x = 1/3 × 7/4
x = 7/12
x : 2/5 = 2/9
x = 2/9 × 2/5
x = 4/45
20 × 7 : ( 5 × x - 3 × 5 ) = 4
140 : 5 × ( x - 3 ) = 4
5 × ( x - 3 ) = 140 : 4
5 × ( x - 3 ) = 35
x - 3 = 35 : 5
x - 3 = 7
x = 7 + 3
x = 10
x - 270 = 420 : 105
x - 270 = 4
x = 4 + 270
x = 274
x - 140 : 35 = 270
x - 4 = 270
x = 270 + 4
x = 274
x + 1/3 = 4/5
x = 4/5 - 1/3
x = 7/15
x - 1/2 = 2/7
x = 2/7 + 1/2
x = 11/14
4/7 * x = 1/3
x = 1/3 : 4/7
x = 7/12
x : 2/5 = 2/9
x = 2/9 * 2/5
x 4 / 45
20 * 7 : ( 5*x - 3 * 5) =4
= 140 :(5*x -3 *5) =4
5*x- 3*5 = 140 : 4
5*x - 3 * 5 = 35
5* x = 35 + 3 * 5
5 * x = 50
x = 50 : 5
x = 10
x - 270 = 402 : 105
x - 270 = 4
x = 270 + 4
x = 274
x- 140 : 35 = 270
x - 4 = 270
x = 270 + 4
x = 274
\(x\cdot1+x\cdot2+x\cdot3=900-420\)
\(x\cdot(1+2+3)=480\)
\(x\cdot6=480\rightarrow x=80\)
X x 1 + X x 2 + X x 3 = 900 - 420
X x ( 1 + 2 + 3 ) = 480
X x 6 = 480
X = 480 : 6
X = 80
a - 420 : ( x : 39 ) = 105
⇒ x : 39 = 420 : 105
⇒ x : 39 = 4
⇒ x = 4 * 39
⇒ x = 156
a) -420 :(x:39)=105
x:39=-420 : 105
x : 39=\(\dfrac{-14}{5}\)
x=\(\dfrac{-546}{5}\)
Cau a các bạn đã làm mình làm câu b , c nhé
420 + 65 x 24 = (x+175) : 5 +30
1980 = (x+175) : 5 + 30
(x+175):5 = 1950
x+175 = 390
x = 215
7 x X - 24 = 5x X
=> 7 x X - 5 x X = 24
2x = 24
=> x = 12
Xx2+Xx7+X=420
Xx(2+7+1)=420
Xx10=420
X=420:10
X=42
Vậy X=42.
x*2+x*3+x*4+x*1=120
x*(2+3+4+1)=420
x*10=420
x= 420:10
x=42
= X x 2 + X x 3 + X x 4 + X x 1 = 420
= X x ( 2 + 3 + 4 + 1 ) = 420
= X x 10 = 420
= 420 : 10
= 42