Pair of Linear Equations in Two Variables — Important Questions
13 hand-picked CBSE Class 10 Maths important questions for Pair of Linear Equations in Two Variables, each with a full model answer — the formats and topics most likely to appear in your board exam.
- 13
- Questions
- 6
- Question types
- 32
- Total marks
- ₹0
- With answers
Focus on the consistency conditions comparing (unique / no / infinite solutions), finding for parallel or coincident lines, graphical solutions with triangle areas, and word problems on fractions, ages, speed–stream and cost solved by substitution or elimination.
About Pair of Linear Equations in Two Variables
A pair is pictured as two straight lines. Comparing the ratios of the coefficients tells you at a glance whether they intersect once, coincide, or are parallel, while substitution and elimination convert real-life situations into solvable systems.
Key concepts & formulas
For and : a unique solution (intersecting lines) if ; infinitely many (coincident) if ; no solution (parallel) if .
Make the coefficients of one variable equal by multiplying, then add or subtract to eliminate that variable. It is usually the fastest route for board word problems.
Equations such as become linear on substituting ; solve for and then back-substitute to get .
Assign a variable to each unknown and turn every sentence into one equation. Common templates: speed (boat–stream: upstream , downstream ); a two-digit number .
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Important questions with answers
Try each on paper first, then reveal the model answer to check your method.
| Question type | Count | Marks |
|---|---|---|
| MCQ | 4 | 1 |
| Assertion–Reason | 1 | 1 |
| Very Short | 2 | 2 |
| Short Answer | 3 | 3 |
| Long Answer | 2 | 5 |
| Case-based | 1 | 4 |
Multiple-choice questions (1 mark)
The pair of equations and has:
- (a)
a unique solution
- (b)
exactly two solutions
- (c)
infinitely many solutions
- (d)
no solution
Show model answer
Answer: (c) infinitely many solutions — . All three ratios are equal, so the lines are coincident.
The graph below shows two lines representing a pair of linear equations. The pair is:
- (a)
consistent with a unique solution
- (b)
inconsistent
- (c)
consistent with infinitely many solutions
- (d)
dependent
Show model answer
Answer: (a) consistent with a unique solution — The two lines intersect at exactly one point , so the system is consistent and has a unique solution.
The value of for which the pair and has infinitely many solutions is:
- (a)
- (b)
- (c)
- (d)
Show model answer
Answer: (c) — For infinitely many solutions . From : . This also satisfies . ✓
The pair of equations and has no solution for:
- (a)
- (b)
all
- (c)
- (d)
all real
Show model answer
Answer: (b) all — Here and are equal. For no solution we need , i.e. .
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Practise free with the AI tutor →Assertion–Reason questions (1 mark)
Assertion (A): The pair of equations and has no solution.
Reason (R): A pair of linear equations has no solution when .
- (a)
Both A and R are true and R is the correct explanation of A
- (b)
Both A and R are true but R is not the correct explanation of A
- (c)
A is true but R is false
- (d)
A is false but R is true
Show model answer
Answer: (a) Both are true and R explains A. The ratios are but , so the lines are parallel and the system has no solution.
Very short answer questions (2 marks)
For what value of will the lines and be parallel?
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For parallel lines (with the constant ratio unequal). Thus .
Solve the pair of equations and . Hence find the value of .
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Adding the two equations: . Then .
So .
Short answer questions (3 marks)
A fraction becomes when is subtracted from its numerator, and it becomes when is added to its denominator. Find the fraction. (CBSE 2023)
Show model answer
Let the fraction be .
Subtracting (i) from (ii): . Then .
The fraction is .
Solve for and : and .
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Let and : , .
Multiply (i) by and (ii) by : and . Adding: .
From (i): .
So and .
A boat goes km upstream and km downstream in hours. In hours it can go km upstream and km downstream. Find the speed of the boat in still water and the speed of the stream.
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Let the boat's speed km/h and the stream's speed km/h. Put and .
, .
Multiply (i) by and (ii) by : and . Subtracting: .
From (i): .
Solving: . Boat km/h, stream km/h.
Long answer questions (5 marks)
Solve graphically the pair of equations and . Shade the triangle formed by these two lines and the -axis, and find its area.
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For : points and . For , i.e. : points and .
The lines meet where and ; adding, . So they intersect at .
The triangle formed with the -axis has vertices and , with base units and height units.
Places and are km apart on a highway. One car starts from and another from at the same time. If the cars travel in the same direction at different speeds, they meet in hours; if they travel towards each other, they meet in hour. Find the speeds of the two cars.
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Let the speeds be km/h and km/h with .
Same direction (relative speed ): km covered in h .
Opposite directions (relative speed ): .
Adding (i) and (ii): ; then .
The speeds are km/h and km/h.
Case-based questions (4 marks)
A taxi service charges a fixed amount plus a rate per kilometre. Riya paid ₹ for a km ride and ₹ for a km ride.
(i) Taking the fixed charge as ₹ and the per-kilometre rate as ₹, form the pair of linear equations.
(ii) Find the fixed charge and the rate per kilometre.
(iii) How much will a km ride cost?
Show model answer
(i) and .
(ii) Subtracting (i) from (ii): . Then . So the fixed charge is ₹ and the rate is ₹ per km.
(iii) Cost of a km ride ₹.
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