Exercise 8A
Page-107
Q1 | Ex-8A | Class 8 | RS AGGARWAL | Linear Equations Solution | myhelper
Question 1:
Solve:
8x + 3 = 27 + 2x
Answer 1:
8x + 3 = 27 + 2x
⇒ 8x - 2x = 27 - 3
⇒ 6x = 24
⇒ x = 246= 4
∴ x=4
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Question 2:
Solve:
5x + 7 = 2x − 8
Answer 2:
5x + 7 = 2x - 8
⇒ 5x - 2x = -8 -7
⇒ 3x = -15
⇒ x = -153= -5
∴ x = -5
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Question 3:
Solve:
2z − 1 = 14 − z
Answer 3:
2z - 1 = 14 - z
⇒ 2z + z = 14 + 1
⇒ 3z = 15
⇒ z= 153= 5
∴ z = 5
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Question 4:
Solve:
9x + 5 = 4(x − 2) + 8
Answer 4:
9x+ 5 = 4( x-2) + 8
⇒ 9x + 5 = 4x - 8 + 8
⇒ 9x + 5 = 4x
⇒ 9x - 4x = -5
⇒ 5x = -5
⇒ x= -55 = -1
∴ x = -1
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Question 5:
Solve:
7y5=y-4
Answer 5:
7y5= y - 4
By cross multiplication:
⇒ 7y = 5(y - 4)
⇒ 7y = 5y - 20
⇒ 7y - 5y =-20
⇒ 2y = -20
⇒ y = -202= -10
∴ y = -10
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Question 6:
Solve:
3x+23=2x+1
Answer 6:
3x + 23 = 2x + 1
⇒ 3x - 2x = 1 - 23
⇒ x = 11 - 23
(L.C.M. of 1 and 3 is 3)
⇒ x = 3 - 23
⇒ x = 13
⇒ x = 13
∴ x = 13
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Question 7:
Solve:
15(y − 4) − 2(y − 9) + 5(y + 6) = 0
Answer 7:
15 (y - 4) - 2 (y - 9) +5 (y + 6) = 0
⇒ 15y - 60 - 2y + 18 + 5y + 30 = 0
⇒15y - 2y + 5y -60 + 18 + 30 = 0
⇒18y - 12 = 0
⇒ 18y = 12
⇒ y = 1218= 23
∴ y = 23
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Question 8:
Solve:
3(5x − 7) − 2(9x − 11) = 4(8x − 13) − 17
Answer 8:
3(5x - 7) - 2(9x - 11) = 4(8x - 13) - 17
⇒15x - 21 - 18x + 22 = 32x - 52 - 17
⇒15x -18x - 21 + 22 = 32x -69
⇒-3x +1 = 32x -69
⇒1 + 69 = 32x + 3x
⇒ 70 = 35x
⇒ 35x= 70
(by transposition)
⇒ x= 7035= 2
∴ x= 2
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Question 9:
Solve:
x-52-x-35=12
Answer 9:
x - 52 - x - 35 = 12
⇒ 10 (x - 52) - 10 (x - 35) = 10 (12)
(multiplying throughout by 10, which is the L.C.M. of 2, 2 and 5)
⇒ 5 (x - 5) -2 (x - 3) = 5
⇒ 5x - 25 - 2x +6 = 5
⇒ 5x - 2x -25 +6 = 5
⇒ 3x -19 = 5
⇒ 3x= 5 + 19
⇒ 3x = 24
⇒ x = 243= 8
∴ x = 8
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Question 10:
Solve:
3t-24-2t+33=23-t
Answer 10:
3t - 24 - 2t + 33 = 23 - t
⇒ 3t - 24 - 2t + 33 = 2 - 3t3
(3 is the L.C.M. of 1 and 3)
⇒ 12 (3t - 24) - 12 ( 2t + 33) = 12 (2 - 3t3)
(multiplying throughout by 12, which is the L.C.M. of 4, 3 and 3)
⇒ 3 (3t - 2) - 4 (2t + 3) = 4( 2 - 3t)
⇒ 9t - 6 - 8t - 12 = 8 - 12t
⇒ 9t - 8t - 6 - 12 = 8 - 12t
⇒ t - 18 = 8 - 12t
⇒ t + 12t = 18 + 8
⇒ 13t = 26
⇒ t = 2613 = 2
∴ t = 2
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Question 11:
Solve:
2x+75-3x+112=2x+83-5
Answer 11:
2x + 75 - 3x + 112 = 2x + 83 - 5
⇒ 2x + 75 - 3x + 112 = 2x + 8 - 153
(L.C.M. of 3 and 1 is 3)
⇒ 30 (2x + 75) - 30 ( 3x + 112) = 30 (2x + 8 - 153)
(multiplying throughout by 30, which is the L.C.M. of 5, 2 and 3)
⇒ 6 (2x + 7) - 15 (3x + 11) = 10 (2x + 8 - 15)
⇒ 12x + 42 - 45x - 165 = 20x -70
⇒ 12x - 45x + 42 - 165 = 20x -70
⇒-33x - 123 = 20x -70
⇒-33x - 20 x = 123 - 70
⇒ -53x = 53
⇒ x = 53-53
⇒ x = -1∴ x = -1
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Question 12:
Solve:
5x-46=4x+1-3x+102
Answer 12:
5x - 46 = 4x + 1 - 3x + 102
⇒ 5x - 46= 2 (4x + 1) - 3x - 102
(L.C.M. of 1 and 2 is 2)
⇒ 5x - 46 = 8x + 2 - 3x - 102
⇒ 5x - 46 = 8x - 3x + 2 - 102
⇒ 5x - 46 = 5x -82
⇒ 2 ( 5x - 4) = 6 (5x -8)
⇒ 10x - 8 = 30x -48
⇒ 10x - 30x = -48 + 8
⇒-20x = -40
⇒x = -40-20= 2∴ x = 2
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Question 13:
Solve:
5x-13(x+1)=6(x+130)
Answer 13:
5x - 13(x + 1) = 6 (x + 130)
⇒ 5x - 1(x + 1)3 = 6 (30x + 130)
(L.C.M. of 1 and 30 is 30)
⇒ 5x - (x + 1)3 = 30x + 15
⇒ 15x - x - 13= 30x + 15
(L.C.M. of 1 and 3 is 3)
⇒ 14x -13 = 30x + 15
⇒ 5 ( 14x - 1) = 3 ( 30x + 1)
(by cross multiplication)
⇒ 70 x -5 = 90 x + 3
⇒ 70x - 90x = 3 +5
⇒ -20x = 8
⇒ x = 8-20 = -25∴ x =-25
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Question 14:
Solve:
4-2(z-43=12(2z+5)
Answer 14:
4 - 2( z-4 )3 = 12( 2z+5 )
⇒ 12 - 2( z-4)3 = 1( 2z+5)2
(L.C.M.
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Question 15:
Solve:
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Solve:
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Solve:
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Solve:
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Solve:
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Solve:
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