Pair of Linear Equations in Two Variables: 1 mark Questions (CBSE Class 10)
68 different 1 mark questions on Pair of Linear Equations in Two Variables from CBSE Class 10 Maths board exams 2022–2026, newest first.
If a pair of linear equations in two variables is represented by two coincident lines, then the pair of equations has :
(A) a unique solution(B) two solutions(C) no solution(D) an infinite number of solutions
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Answer: (D) an infinite number of solutions
Coincident lines have every point in common. Every common point is a solution, so the pair has infinitely many solutions.
If the pair of linear equations : a 1 x + b 1 y + c 1 = 0 and a 2 x + b 2 y + c 2 = 0 is consistent and dependent, then
(A) a 2 a 1 = b 2 b 1 (B) a 2 a 1 = b 2 b 1 = c 2 c 1 (C) a 2 a 1 = b 2 b 1 = c 2 c 1 (D) a 2 a 1 = b 2 b 1 = c 2 c 1
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Answer: (D) a 2 a 1 = b 2 b 1 = c 2 c 1
A consistent and dependent pair represents coincident lines. For coincident lines, a 2 a 1 = b 2 b 1 = c 2 c 1 .
The pair of linear equations 2 3 x + 3 5 y = 7 and 9 x + 10 y = 14 , is :
(A) consistent(B) inconsistent(C) consistent with one solution(D) consistent with many solutions
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Answer: (B) inconsistent
Multiplying the first equation by 6: 9 x + 10 y = 42 . Compare with 9 x + 10 y = 14 : 9 9 = 10 10 = 14 42 . The lines are parallel, so the pair is inconsistent.
Equation of another line parallel to the line represented by 2 x − 6 y = 7 is :
(A) y = 3 x − 7 (B) 2 x = 9 − 6 y (C) x − 3 y = 7 (D) x = 2 7 − 3 y
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Answer: (C) x − 3 y = 7
Parallel lines need a 2 a 1 = b 2 b 1 = c 2 c 1 For x − 3 y = 7 and 2 x − 6 y = 7 : 2 1 = − 6 − 3 = 2 1 and 7 7 = 1 = 2 1 , so parallel (A) is 3 x − y = 7 , (B) is 2 x + 6 y = 9 , (D) is 2 x + 6 y = 7 : none of these has the right ratio
Equation of a line coincident with 2.5 x − 2 y = 3 is :
(A) 5 x − 4 y = 3 (B) 5 x − 4 y + 6 = 0 (C) 15 x − 12 y − 3 = 0 (D) 5 x − 4 y − 6 = 0
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Answer: (D) 5 x − 4 y − 6 = 0
Multiply 2.5 x − 2 y = 3 by 2: 5 x − 4 y = 6 , i.e. 5 x − 4 y − 6 = 0 Coincident lines need a 2 a 1 = b 2 b 1 = c 2 c 1 , which holds only for (D)
The value of k for which the system of linear equations 2 x + 3 y = 5 and 2 x + k y = 7 is inconsistent, is
(A) 4 3 (B) 3 4 (C) 3 1 (D) 3
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Answer: (B) 3 4
Inconsistent: a 2 a 1 = b 2 b 1 = c 2 c 1 . 2 1/2 = k 1/3 ⇒ 4 1 = 3 k 1 ⇒ k = 3 4 Check: c 2 c 1 = 7 5 = 4 1 , so the system is inconsistent.
The value of k for which the system of linear equations k x − y − 2 = 0 and 6 x − 2 y − 3 = 0 has infinitely many solutions, is (does)
(A) 2 1 (B) 3(C) 4(D) Not exist
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Answer: (D) Not exist
Infinitely many solutions need a 2 a 1 = b 2 b 1 = c 2 c 1 . b 2 b 1 = − 2 − 1 = 2 1 but c 2 c 1 = − 3 − 2 = 3 2 .Since b 2 b 1 = c 2 c 1 , no value of k works (k = 3 makes the lines parallel). Such k does not exist.
Assertion (A): The system of linear equations 3 x − 5 y + 7 = 0 and − 6 x + 10 y + 14 = 0 is inconsistent. Reason (R): When two linear equations don’t have unique solution, they always represent parallel lines.
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).(C) Assertion (A) is true, but Reason (R) is false.(D) Assertion (A) is false, but Reason (R) is true.
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Answer: (C) Assertion (A) is true, but Reason (R) is false.
a 2 a 1 = − 6 3 = − 2 1 , b 2 b 1 = 10 − 5 = − 2 1 , c 2 c 1 = 14 7 = 2 1 a 2 a 1 = b 2 b 1 = c 2 c 1 , so the lines are parallel and the system is inconsistent. A is true.If there is no unique solution, the lines may be parallel or coincident (infinitely many solutions). So R is false.
Assertion (A) : The value of p for which the system of equations 4 x + p y + 8 = 0 and 2 x + 2 y + 2 = 0 is consistent is 4. Reason (R) : The system of equations a 1 x + b 1 y = c 1 and a 2 x + b 2 y = c 2 is consistent with infinitely many solutions, if a 2 a 1 = b 2 b 1 = c 2 c 1 .
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).(C) Assertion (A) is true, but Reason (R) is false.(D) Assertion (A) is false, but Reason (R) is true.
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Answer: (D) Assertion (A) is false, but Reason (R) is true.
For p = 4 : a 2 a 1 = 2 4 = 2 , b 2 b 1 = 2 4 = 2 , c 2 c 1 = 2 8 = 4 . Since a 2 a 1 = b 2 b 1 = c 2 c 1 , the lines are parallel and the system is inconsistent. So A is false. R is the standard condition for infinitely many solutions, so R is true.
If (0, 0) is the solution of the equation x + y = c − 1 , then the value of c is :
(A) 0 (B) 1 (C) − 1 (D) any real number
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Answer: (B) 1
Put x = 0 , y = 0 : 0 + 0 = c − 1 . So c = 1 .
The number of solutions of the system of equations x = 3 , y = − 1 is :
(A) 0 (B) 1 (C) 2 (D) Infinite
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Answer: (B) 1
x = 3 is a vertical line and y = − 1 is a horizontal line.They intersect at exactly one point (3, − 1 ), so there is one solution.
The number of solutions of the system of equations x = a , x = b ( a = b ) is :
(A) 0 (B) 1 (C) 2 (D) Infinite
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Answer: (A) 0
x = a and x = b are two distinct lines parallel to the y-axis.Parallel lines never meet, so there is no solution.
For what value(s) of k does the system of equations k x + 2 y = 3 and 2 x + y = 5 have a unique solution ?
(A) k = a real number(B) k = 8 (C) k = 4 (D) k = 4
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Answer: (C) k = 4
For a unique solution, a 2 a 1 = b 2 b 1 . 2 k = 1 2 , so k = 4 .
For what value(s) of k , is the system of equations k x + 2 y = 3 and 2 x + y = 5 inconsistent ?
(A) k = Any real number(B) k = 2 (C) k = 4 (D) k = 4
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Answer: (D) k = 4
For no solution: a 2 a 1 = b 2 b 1 = c 2 c 1 . 2 k = 1 2 ⇒ k = 4 .Check: 1 2 = 5 3 , so with k = 4 the system is inconsistent.
The system of linear equations given by x = a and y = b is :
(A) Consistent with a unique solution.(B) Consistent with infinitely many solutions.(C) Consistent with two solutions.(D) Inconsistent.
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Answer: (A) Consistent with a unique solution.
x = a is a line parallel to the y-axis and y = b is a line parallel to the x-axis.These lines are perpendicular and meet at exactly one point ( a , b ) . So the system is consistent with a unique solution.
The value of m for which lines 14 x + m y = 20 and − 3 x + 2 y = 16 are parallel, is :
(A) − 14 3 (B) − 3 7 (C) − 3 28 (D) − 28 3
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Answer: (C) − 3 28
For parallel lines, a 2 a 1 = b 2 b 1 = c 2 c 1 . − 3 14 = 2 m , so m = − 3 28 .Check: c 2 c 1 = 16 20 = − 3 14 , so the lines are parallel.
The line 2 x − 3 y = 6 intersects x – axis at
(A) (0, − 2 )(B) (0, 3)(C) (− 2 , 0)(D) (3, 0)
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Answer: (D) (3, 0)
On the x -axis, y = 0 . 2 x = 6 , so x = 3 . The point is (3, 0).
The value of k for which the system of equations 3 x − 7 y = 1 and k x + 14 y = 6 is inconsistent, is
(A) − 6 (B) 3 2 (C) 6(D) 2 − 3
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Answer: (A) − 6
Inconsistent when k 3 = 14 − 7 = 6 1 . k 3 = − 2 1 gives k = − 6 , and − 2 1 = 6 1 .
The point (3, − 5) lies on the line m x − y = 11 . The value of m is
(A) 3(B) − 2 (C) 8(D) 2
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Answer: (D) 2
Substitute x = 3 , y = − 5 : 3 m + 5 = 11 . 3 m = 6 , so m = 2 .
If x = 1 and y = 2 is a solution of the pair of linear equations 2 x − 3 y + a = 0 and 2 x + 3 y − b = 0 , then :
(A) a = 2 b (B) 2 a = b (C) a + 2 b = 0 (D) 2 a + b = 0
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Answer: (B) 2 a = b
Put x = 1 , y = 2 in 2 x − 3 y + a = 0 : 2 − 6 + a = 0 , so a = 4 . Put x = 1 , y = 2 in 2 x + 3 y − b = 0 : 2 + 6 − b = 0 , so b = 8 . Hence b = 2 a , i.e. 2 a = b .
The line represented by the equation x − y = 0 is :
(A) parallel to x-axis(B) parallel to y-axis(C) passing through the origin(D) passing through the point ( 3 , 2 )
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Answer: (C) passing through the origin
At x = 0 , y = 0 , so ( 0 , 0 ) satisfies x − y = 0 The line y = x passes through the origin (it is neither horizontal nor vertical, and ( 3 , 2 ) does not satisfy it)
The equation of a line parallel to the x-axis and at a distance of 3 units below x-axis is :
(A) x = 3 (B) x = − 3 (C) y = − 3 (D) y = 3
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Answer: (C) y = − 3
A line parallel to the x-axis has equation y = c 3 units below the x-axis means c = − 3 , so y = − 3
Assertion (A) : The pair of linear equations p x + 3 y + 59 = 0 and 2 x + 6 y + 118 = 0 will have infinitely many solutions if p = 1 . Reason (R) : If the pair of linear equations p x + 3 y + 19 = 0 and 2 x + 6 y + 157 = 0 has a unique solution, then p = 1 .
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).(C) Assertion (A) is true, but Reason (R) is false.(D) Assertion (A) is false, but Reason (R) is true.
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Answer: (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
A: with p = 1 , 2 1 = 6 3 = 118 59 = 2 1 , so infinitely many solutions; A is true R: unique solution needs 2 p = 6 3 , i.e. p = 1 ; R is true R is about a different pair and the unique-solution condition, so it does not explain A
The equation of a line parallel to y-axis and at a distance of 5 units to the right of y-axis is :
(A) x = 5 (B) x = − 5 (C) y = 5 (D) y = − 5
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Answer: (A) x = 5
A line parallel to the y-axis has equation x = c 5 units to the right of the y-axis means c = 5 , so x = 5
The value of 'k' for which the system of linear equations 6 x + y = 3 k and 36 x + 6 y = 3 have infinitely many solutions is :
(A) 6(B) 6 1 (C) 2 1 (D) 3 1
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Answer: (B) 6 1
For infinitely many solutions, a 2 a 1 = b 2 b 1 = c 2 c 1 . 36 6 = 6 1 = 3 3 k .So k = 6 1 .
A system of two linear equations in two variables is inconsistent, if the lines in the graph are :
(A) coincident(B) parallel(C) intersecting at one point(D) intersecting at right angles
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Answer: (B) parallel
An inconsistent system has no solution. Two lines have no common point only when they are parallel (distinct).
The value of 'p ' for which the equations p x + 3 y = p − 3 , 12 x + p y = p has infinitely many solutions is :
(A) − 6 only(B) 6 only(C) ± 6 (D) Any real number except ± 6
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Answer: (B) 6 only
Infinitely many solutions: 12 p = p 3 = p p − 3 12 p = p 3 ⇒ p 2 = 36 ⇒ p = ± 6 p 3 = p p − 3 ⇒ p − 3 = 3 ⇒ p = 6 So p = 6 only (check: 12 6 = 6 3 = 6 3 ).
The system of equations 2 x + 1 = 0 and 3 y − 5 = 0 has
(A) unique solution(B) two solutions(C) no solution(D) infinite number of solutions
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Answer: (A) unique solution
2 x + 1 = 0 ⇒ x = − 2 1 (a line parallel to the y -axis)3 y − 5 = 0 ⇒ y = 3 5 (a line parallel to the x -axis)The lines intersect at exactly one point ( − 2 1 , 3 5 ) , so a unique solution.
The system of equations x + 5 = 0 and 2 x − 1 = 0 , has
(A) No solution(B) Unique solution(C) Two solutions(D) Infinite solutions
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Answer: (A) No solution
x + 5 = 0 ⇒ x = − 5 and 2 x − 1 = 0 ⇒ x = 2 1 Both are lines parallel to the y -axis, at different positions, so they never meet. No value of x satisfies both, so the system has no solution.
The system of equations y + a = 0 and 2 x = b has
(A) No solution(B) ( − a , 2 b ) as its solution(C) ( 2 b , − a ) as its solution(D) Infinite solutions
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Answer: (C) ( 2 b , − a ) as its solution
y + a = 0 ⇒ y = − a ; 2 x = b ⇒ x = 2 b The lines are perpendicular to each other and meet at exactly one point ( 2 b , − a ) .
The value of k for which the pair of linear equations 5 x + 2 y − 7 = 0 and 2 x + k y + 1 = 0 don't have a solution, is :
(A) 5(B) 5 4 (C) 4 5 (D) 2 5
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Answer: (B) 5 4
No solution when a 2 a 1 = b 2 b 1 = c 2 c 1 . 2 5 = k 2 gives k = 5 4 .Check: c 2 c 1 = 1 − 7 = − 7 = 2 5 , so there is no solution.
The value of ‘k’ for which the pair of linear equations x + y − 4 = 0 and 2 x + k y − 8 = 0 has infinitely many solutions, is
(A) k = 2 (B) k = − 2 (C) k = 2 (D) k = − 2
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Answer: (C) k = 2
For infinitely many solutions, a 2 a 1 = b 2 b 1 = c 2 c 1 . 2 1 = k 1 = − 8 − 4 So k = 2 .
The graph of a pair of linear equations a 1 x + b 1 y = c 1 and a 2 x + b 2 y = c 2 in two variables x and y represents parallel lines, if
(A) a 2 a 1 = b 2 b 1 (B) a 2 a 1 = b 2 b 1 = c 2 c 1 (C) a 2 a 1 = b 2 b 1 = c 2 c 1 (D) a 2 a 1 = b 2 b 1 = c 2 c 1
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Answer: (D) a 2 a 1 = b 2 b 1 = c 2 c 1
Lines are parallel when the pair is inconsistent. This happens when a 2 a 1 = b 2 b 1 = c 2 c 1 .
The value of ‘p’ for which the pair of equations − 2 x + 3 y − 9 = 0 and 4 x + p y + 7 = 0 has a unique solution is
(A) p = 6 (B) p = 6 (C) p = − 6 (D) p = − 6
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Answer: (D) p = − 6
Unique solution needs a 2 a 1 = b 2 b 1 . 4 − 2 = p 3 ⇒ − 2 p = 12 ⇒ p = − 6
The lines represented by linear equations x = a and y = b ( a = b ) are
(A) intersecting at (a, b).(B) intersecting at (b, a).(C) parallel.(D) coincident.
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Answer: (A) intersecting at (a, b).
x = a is a line parallel to the y-axis and y = b is a line parallel to the x-axis.They meet at the point whose x-coordinate is a and y-coordinate is b , i.e. ( a , b ) .
Assertion (A): The pair of linear equations 5 x + 2 y + 6 = 0 and 7 x + 6 y + 18 = 0 have infinitely many solutions. Reason (R): The pair of linear equations a 1 x + b 1 y + c 1 = 0 and a 2 x + b 2 y + c 2 = 0 have infinitely many solutions, if a 2 a 1 = b 2 b 1 = c 2 c 1 .
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).(C) Assertion (A) is true, but Reason (R) is false.(D) Assertion (A) is false, but Reason (R) is true.
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Answer: (D) Assertion (A) is false, but Reason (R) is true.
a 2 a 1 = 7 5 , b 2 b 1 = 6 2 = 3 1 .Since 7 5 = 3 1 , the pair has a unique solution, so A is false. R is the correct condition for infinitely many solutions, so R is true. Answer (D).
The pair of linear equations 2 k x + 5 y = 7 , 6 x + 5 y = 11 have a unique solution, if
(A) k = 3 (B) k = − 3 (C) k = 3 1 (D) k = − 3 1
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Answer: (A) k = 3
For a unique solution, a 2 a 1 = b 2 b 1 . 6 2 k = 5 5 , so 2 k = 6 .Hence k = 3 .
In the given figure, graphs of two linear equations are shown. The pair of these linear equations is :
(A) consistent with unique solution.(B) consistent with infinitely many solutions.(C) inconsistent.(D) inconsistent but can be made consistent by extending these lines.
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Answer: (A) consistent with unique solution.
The two lines in the figure have different slopes, so they are not parallel. Non-parallel lines intersect in exactly one point (here, when extended to the left). Hence the pair is consistent with a unique solution.
The value of k for which the system of equations 3 x − y + 8 = 0 and 6 x − k y + 16 = 0 has infinitely many solutions, is
(A) − 2 (B) 2(C) 2 1 (D) − 2 1
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Answer: (B) 2
For infinitely many solutions, a 2 a 1 = b 2 b 1 = c 2 c 1 . 6 3 = − k − 1 = 16 8 , so k 1 = 2 1 .k = 2
The pair of linear equations x + 2 y + 5 = 0 and − 3 x = 6 y − 1 has
(A) unique solution(B) exactly two solutions(C) infinitely many solutions(D) no solution
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Answer: (D) no solution
Write both in standard form: x + 2 y + 5 = 0 and 3 x + 6 y − 1 = 0 . a 2 a 1 = 3 1 , b 2 b 1 = 6 2 = 3 1 , c 2 c 1 = − 1 5 = − 5 .a 2 a 1 = b 2 b 1 = c 2 c 1 , so the lines are parallel.The pair has no solution.
If a pair of linear equations in two variables is consistent, then the lines represented by the two equations are :
(A) always intersecting(B) parallel(C) always coincident(D) intersecting or coincident
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Answer: (D) intersecting or coincident
A consistent pair has at least one solution. Intersecting lines give exactly one solution and coincident lines give infinitely many; parallel lines give none. So the lines are intersecting or coincident.
If a x + b y = a 2 − b 2 and b x + a y = 0 , then the value of x + y is :
(A) a 2 − b 2 (B) a + b (C) a − b (D) a 2 + b 2
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Answer: (C) a − b
Add the two equations: ( a + b ) x + ( a + b ) y = a 2 − b 2 . ( a + b ) ( x + y ) = ( a + b ) ( a − b ) .Divide by a + b (assumed non-zero): x + y = a − b .
Two lines are given to be parallel. The equation of one of these lines is 5 x − 3 y = 2 . The equation of the second line can be :
(A) − 15 x − 9 y = 5 (B) 15 x + 9 y = 5 (C) 9 x − 15 y = 6 (D) − 15 x + 9 y = 5
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Answer: (D) − 15 x + 9 y = 5
For parallel lines, a 2 a 1 = b 2 b 1 = c 2 c 1 . With − 15 x + 9 y = 5 : − 15 5 = − 3 1 , 9 − 3 = − 3 1 , 5 2 = − 3 1 . So − 15 x + 9 y = 5 is parallel to 5 x − 3 y = 2 . (The other options fail a 2 a 1 = b 2 b 1 .)
The pair of linear equations y = 0 and y = − 7 have
(A) exactly one solution(B) two solutions(C) infinitely many solutions(D) no solution
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Answer: (D) no solution
y = 0 is the x-axis and y = − 7 is a line parallel to it. Parallel distinct lines never meet. So the pair has no solution.
Which out of the following type of straight lines will be represented by the system of equations 3 x + 4 y = 5 and 6 x + 8 y = 7 ?
(A) Parallel(B) Intersecting(C) Coincident(D) Perpendicular to each other
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Answer: (A) Parallel
a 2 a 1 = 6 3 = 2 1 , b 2 b 1 = 8 4 = 2 1 , c 2 c 1 = 7 5 .a 2 a 1 = b 2 b 1 = c 2 c 1 , so the lines are parallel.
The larger of two supplementary angles exceeds the smaller by 18 degrees. What is the measure of larger angle ?
(A) 8 1 ∘ (B) 9 9 ∘ (C) 3 6 ∘ (D) 5 4 ∘
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Answer: (B) 9 9 ∘
Let the larger angle be x and the smaller be y . x + y = 180 and x − y = 18 .Adding: 2 x = 198 , so x = 9 9 ∘ .
Assertion (A) : The system of linear equations 3 x + 5 y − 4 = 0 and 15 x + 25 y − 25 = 0 is inconsistent. Reason (R) : The pair of linear equations a 1 x + b 1 y + c 1 = 0 and a 2 x + b 2 y + c 2 = 0 is inconsistent if a 2 a 1 = b 2 b 1 = c 2 c 1 .
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).(B) Both Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).(C) Assertion (A) is true, but Reason (R) is false.(D) Assertion (A) is false, but Reason (R) is true.
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Answer: (A) Both A and R are true and R is the correct explanation of A.
R is the standard condition for no solution, so R is true. For A: a 2 a 1 = 15 3 = 5 1 , b 2 b 1 = 25 5 = 5 1 , c 2 c 1 = − 25 − 4 = 25 4 . 5 1 = 5 1 = 25 4 , so the system is inconsistent; A is true.A follows from the condition in R, so R correctly explains A.
The pair of linear equations x + 2 y − 5 = 0 and 2 x − 4 y + 6 = 0 :
(A) is inconsistent(B) is consistent with many solutions(C) is consistent with a unique solution(D) is consistent with two solutions
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Answer: (c) is consistent with a unique solution
a 2 a 1 = 2 1 and b 2 b 1 = − 4 2 = − 2 1 Since a 2 a 1 = b 2 b 1 , the lines intersect at one point. The pair is consistent with a unique solution.
The lines represented by the linear equations y = x and x = 4 intersect at P. The coordinates of the point P are :
(A) (4, 0)(B) (4, 4)(C) (0, 4)(D) ( − 4 , 4 )
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Answer: (b) (4, 4)
At P, x = 4. Since P lies on y = x, y = 4. P = (4, 4)
The pair of linear equations x + 2 y + 5 = 0 and − 3 x − 6 y + 1 = 0 has :
(A) a unique solution(B) exactly two solutions(C) infinitely many solutions(D) no solution
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Answer: (D) no solution
a 2 a 1 = − 3 1 , b 2 b 1 = − 6 2 = − 3 1 , c 2 c 1 = 1 5 = 5 .a 2 a 1 = b 2 b 1 = c 2 c 1 , so the lines are parallel and there is no solution.
If the pair of linear equations x − y = 1 , x + k y = 5 has a unique solution x = 2 , y = 1 , then the value of k is :
(A) − 2 (B) − 3 (C) 3(D) 4
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Answer: (C) 3
Put x = 2 , y = 1 in x + k y = 5 : 2 + k = 5 . So k = 3 .
The value of k for which the equations 3 x − y + 8 = 0 and 6 x − k y + 16 = 0 represent coincident lines is :
(A) 2 1 (B) − 2 1 (C) 2(D) − 2
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Answer: (C) 2
For coincident lines: 6 3 = − k − 1 = 16 8 . k 1 = 2 1 ⇒ k = 2 .
If the lines represented by equations 3 x + 2 m y = 2 and 2 x + 5 y + 1 = 0 are parallel, then the value of m is :
(A) 5 2 (B) − 4 5 (C) 2 3 (D) 4 15
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Answer: (D) 4 15
Write the lines as 3 x + 2 m y − 2 = 0 and 2 x + 5 y + 1 = 0 . For parallel lines, 2 3 = 5 2 m = 1 − 2 . 4 m = 15 , so m = 4 15 .
The value of k, if (6, k) lies on the line represented by x − 3 y + 6 = 0 , is
(A) − 4 (B) 12(C) − 12 (D) 4
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Answer: (D) 4
Put x = 6 , y = k : 6 − 3 k + 6 = 0 . 3 k = 12 , so k = 4 .
The value of ‘k’ for which the system of equations k x + 2 y = 5 and 3 x + 4 y = 1 have no solution, is
(A) k = 2 3 (B) k = 2 3 (C) k = 3 2 (D) k = 15
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Answer: (A) k = 2 3
No solution when a 2 a 1 = b 2 b 1 = c 2 c 1 . 3 k = 4 2 gives k = 2 3 ; and 4 2 = 1 5 .So k = 2 3 .
The value of ‘p’ if (–2, p) lies on the line represented by the equation 2 x − 3 y + 7 = 0 , is
(A) − 2 13 (B) 2 13 (C) − 1 (D) 1
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Answer: (D) 1
Put x = − 2 , y = p : 2 ( − 2 ) − 3 p + 7 = 0 . 3 − 3 p = 0 , so p = 1 .
The value of k for which the pair of equations k x = y + 2 and 6 x = 2 y + 3 has infinitely many solutions,
(A) is k = 3(B) does not exist(C) is k = –3(D) is k = 4
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Answer: (B) does not exist
Write the equations as k x − y − 2 = 0 and 6 x − 2 y − 3 = 0 . For infinitely many solutions: 6 k = − 2 − 1 = − 3 − 2 . But − 2 − 1 = 2 1 and − 3 − 2 = 3 2 are not equal. So no value of k works.
If the pair of equations 3 x − y + 8 = 0 and 6 x − r y + 16 = 0 represent coincident lines, then the value of ‘r’ is :
(A) − 2 1 (B) 2 1 (C) − 2 (D) 2
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Answer: (D) 2
For coincident lines a 2 a 1 = b 2 b 1 = c 2 c 1 . 6 3 = − r − 1 = 16 8 = 2 1 r 1 = 2 1 , so r = 2
The pair of equations x = a and y = b graphically represents lines which are :
(A) parallel(B) intersecting at (b, a)(C) coincident(D) intersecting at (a, b)
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Answer: (D) intersecting at (a, b)
x = a is a line parallel to the y-axis and y = b is a line parallel to the x-axis.They are perpendicular and meet at the point ( a , b ) .
If 2 x + 3 y = 15 and 3 x + 2 y = 25 , then the value of x − y is :
(A) − 10 (B) 8(C) 10(D) − 8
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Answer: (C) 10
Subtract the first equation from the second: ( 3 x + 2 y ) − ( 2 x + 3 y ) = 25 − 15 x − y = 10
The pair of linear equations 2 x = 5 y + 6 and 15 y = 6 x − 18 represents two lines which are :
(A) intersecting(B) parallel(C) coincident(D) either intersecting or parallel
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Answer: (C) coincident
Write as 2 x − 5 y − 6 = 0 and 6 x − 15 y − 18 = 0 . a 2 a 1 = 6 2 = 3 1 , b 2 b 1 = − 15 − 5 = 3 1 , c 2 c 1 = − 18 − 6 = 3 1 All three ratios are equal, so the lines are coincident.
The pair of equations a x + 2 y = 9 and 3 x + b y = 18 represent parallel lines, where a, b are integers, if :
(A) a = b (B) 3 a = 2 b (C) 2 a = 3 b (D) ab = 6
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Answer: (D) ab = 6
For parallel lines, a 2 a 1 = b 2 b 1 = c 2 c 1 . 3 a = b 2 = 18 9 .3 a = b 2 gives ab = 6 (and for integers 3 a = 2 1 always holds).
The solution of the pair of equations x + y = a + b and a x − b y = a 2 − b 2 is :
(A) x = b, y = a(B) x = − a , y = b(C) x = a, y = b(D) x = a, y = − b
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Answer: (C) x = a, y = b
Multiply the first equation by b: b x + b y = ab + b 2 . Add to the second: ( a + b ) x = a 2 + ab = a ( a + b ) , so x = a (taking a + b = 0 ). Then y = (a + b) – a = b. Check: a ⋅ a − b ⋅ b = a 2 − b 2 .
The point of intersection of the line represented by 3 x − y = 3 and y-axis is given by
(A) (0, –3)(B) (0, 3)(C) (2, 0)(D) (–2, 0)
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Answer: (A) (0, –3)
On the y-axis, x = 0 . 3 ( 0 ) − y = 3 gives y = − 3 .The point is (0, –3).
3 chairs and 1 table cost ₹ 900; whereas 5 chairs and 3 tables cost ₹ 2,100. If the cost of 1 chair is ₹ x and the cost of 1 table is ₹ y, then the situation can be represented algebraically as
(A) 3 x + y = 900 , 3 x + 5 y = 2100 (B) x + 3 y = 900 , 3 x + 5 y = 2100 (C) 3 x + y = 900 , 5 x + 3 y = 2100 (D) x + 3 y = 900 , 5 x + 3 y = 2100
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Answer: (C) 3 x + y = 900 , 5 x + 3 y = 2100
3 chairs and 1 table: 3 x + y = 900 . 5 chairs and 3 tables: 5 x + 3 y = 2100 .
The coordinates of the point where the line 2 y = 4 x + 5 crosses x -axis is
(A) ( 0 , 4 − 5 ) (B) ( 0 , 2 5 ) (C) ( 4 − 5 , 0 ) (D) ( 2 − 5 , 0 )
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Answer: (C) ( 4 − 5 , 0 )
On the x-axis, y = 0. 0 = 4 x + 5 , so x = − 4 5 .The point is ( 4 − 5 , 0 ) .
The point of intersection of the line represented by 3 x − y = 3 and the y-axis is given by
(A) (0, –3)(B) (0, 3)(C) (2, 0)(D) (–2, 0)
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Answer: (A) (0, –3)
On the y-axis, x = 0 . 3 ( 0 ) − y = 3 gives y = − 3 .The point is (0, –3).
The condition for the system of linear equations a x + b y = c ; l x + m y = n to have a unique solution is
(A) am = b l (B) a l = bm (C) a l = bm (D) am = b l
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Answer: (A) am = b l
Unique solution when l a = m b . This gives am = b l .
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