Class 10 Exam  >  Class 10 Notes  >  Mathematics (Maths) Class 10  >  RD Sharma Solutions: Pair of Linear Equations in Two Variables - 3

Pair of Linear Equations in Two Variables - 3 RD Sharma Solutions | Mathematics (Maths) Class 10 PDF Download

Download, print and study this document offline
Please wait while the PDF view is loading
 Page 1


 
 
 
 
 
               Exercise 3.3 
Solve the following systems of equations: 
1. 11x + 15y + 23 = 0 
7x – 2y – 20 = 0 
Sol: 
The given system of equation is 
? ?
? ?
11 15 23 0 ...
7 2 20 0 ...
x y i
x y ii
? ? ?
? ? ?
 
From (ii), we get 
2 7 20
7 20
2
yx
x
y
??
?
??
 
Substituting 
7 20
2
x
y
?
? in (i) we get 
7 20
11 15 23 0
2
105 300
11 23 0
2
22 105 300 46
0
2
127 254 0
127 254
254
2
127
x
x
x
x
xx
x
x
x
? ??
? ? ?
??
??
?
? ? ? ?
? ? ?
??
? ? ?
??
? ? ?
 
Page 2


 
 
 
 
 
               Exercise 3.3 
Solve the following systems of equations: 
1. 11x + 15y + 23 = 0 
7x – 2y – 20 = 0 
Sol: 
The given system of equation is 
? ?
? ?
11 15 23 0 ...
7 2 20 0 ...
x y i
x y ii
? ? ?
? ? ?
 
From (ii), we get 
2 7 20
7 20
2
yx
x
y
??
?
??
 
Substituting 
7 20
2
x
y
?
? in (i) we get 
7 20
11 15 23 0
2
105 300
11 23 0
2
22 105 300 46
0
2
127 254 0
127 254
254
2
127
x
x
x
x
xx
x
x
x
? ??
? ? ?
??
??
?
? ? ? ?
? ? ?
??
? ? ?
??
? ? ?
 
 
Putting 2 x ? in 
7 20
2
x
y
?
? we get 
7 2 20
2
14 20
2
6
2
3
y
??
??
?
?
?
?
??
 
Hence, the solution of the given system of equations is 2, 3. xy ? ? ? 
 
 
 
2. 3x – 7y + 10 = 0 
y – 2x – 3 = 0 
Sol: 
The given system of equation is 
? ?
? ?
3 7 10 0 ...
2 3 0 ...
x y i
y x ii
? ? ?
? ? ?
 
From (ii), we get 
23 yx ?? 
Substituting 23 yx ?? in (i) we get 
? ? 3 7 2 3 10 0
3 14 21 10 0
11 11
11
1
11
xx
xx
x
x
? ? ? ?
? ? ? ? ?
? ? ?
? ? ? ?
?
 
Putting 1 x ?? in 2 3, yx ?? we get 
? ? 2 1 3
23
1
1
y
y
? ? ? ? ?
? ? ?
?
??
 
Hence, the solution of the given system of equations is 1, 1. xy ? ? ? 
 
3. 0.4x + 0.3y = 1.7 
0.7x + 0.2y = 0.8 
Sol: 
Page 3


 
 
 
 
 
               Exercise 3.3 
Solve the following systems of equations: 
1. 11x + 15y + 23 = 0 
7x – 2y – 20 = 0 
Sol: 
The given system of equation is 
? ?
? ?
11 15 23 0 ...
7 2 20 0 ...
x y i
x y ii
? ? ?
? ? ?
 
From (ii), we get 
2 7 20
7 20
2
yx
x
y
??
?
??
 
Substituting 
7 20
2
x
y
?
? in (i) we get 
7 20
11 15 23 0
2
105 300
11 23 0
2
22 105 300 46
0
2
127 254 0
127 254
254
2
127
x
x
x
x
xx
x
x
x
? ??
? ? ?
??
??
?
? ? ? ?
? ? ?
??
? ? ?
??
? ? ?
 
 
Putting 2 x ? in 
7 20
2
x
y
?
? we get 
7 2 20
2
14 20
2
6
2
3
y
??
??
?
?
?
?
??
 
Hence, the solution of the given system of equations is 2, 3. xy ? ? ? 
 
 
 
2. 3x – 7y + 10 = 0 
y – 2x – 3 = 0 
Sol: 
The given system of equation is 
? ?
? ?
3 7 10 0 ...
2 3 0 ...
x y i
y x ii
? ? ?
? ? ?
 
From (ii), we get 
23 yx ?? 
Substituting 23 yx ?? in (i) we get 
? ? 3 7 2 3 10 0
3 14 21 10 0
11 11
11
1
11
xx
xx
x
x
? ? ? ?
? ? ? ? ?
? ? ?
? ? ? ?
?
 
Putting 1 x ?? in 2 3, yx ?? we get 
? ? 2 1 3
23
1
1
y
y
? ? ? ? ?
? ? ?
?
??
 
Hence, the solution of the given system of equations is 1, 1. xy ? ? ? 
 
3. 0.4x + 0.3y = 1.7 
0.7x + 0.2y = 0.8 
Sol: 
 
 
 
The given system of equation is 
? ?
? ?
0.4 0.3 1.7 ...
0.7 0.2 0.8 ...
x y i
x y ii
??
??
 
Multiplying both sides of (i) and (ii), by 10, we get 
? ?
? ?
4 3 17 ...
7 2 8 ...
x y iii
x y iv
??
??
 
From (iv), we get 
7 8 2
82
7
7
xy
y
x
??
?
?
 
Substituting 
82
7
y
x
?
? in (iii), we get 
82
4 3 17
7
32 8
3 17
7
32 29 17 7
y
y
y
y
y
? ??
??
??
??
?
? ? ?
? ? ? ?
 
29 119 32
29 87
87
3
29
y
y
y
? ? ?
??
? ? ?
 
Putting 3 y ? in 
82
,
7
y
x
?
? we get 
8 2 3
7
x
??
? 
86
7
14
7
2
?
?
?
?
 
Hence, the solution of the given system of equation is 2, 3. xy ?? 
 
4. 0.8
2
x
y ?? 
Sol: 
0.8
2
x
y ?? 
Page 4


 
 
 
 
 
               Exercise 3.3 
Solve the following systems of equations: 
1. 11x + 15y + 23 = 0 
7x – 2y – 20 = 0 
Sol: 
The given system of equation is 
? ?
? ?
11 15 23 0 ...
7 2 20 0 ...
x y i
x y ii
? ? ?
? ? ?
 
From (ii), we get 
2 7 20
7 20
2
yx
x
y
??
?
??
 
Substituting 
7 20
2
x
y
?
? in (i) we get 
7 20
11 15 23 0
2
105 300
11 23 0
2
22 105 300 46
0
2
127 254 0
127 254
254
2
127
x
x
x
x
xx
x
x
x
? ??
? ? ?
??
??
?
? ? ? ?
? ? ?
??
? ? ?
??
? ? ?
 
 
Putting 2 x ? in 
7 20
2
x
y
?
? we get 
7 2 20
2
14 20
2
6
2
3
y
??
??
?
?
?
?
??
 
Hence, the solution of the given system of equations is 2, 3. xy ? ? ? 
 
 
 
2. 3x – 7y + 10 = 0 
y – 2x – 3 = 0 
Sol: 
The given system of equation is 
? ?
? ?
3 7 10 0 ...
2 3 0 ...
x y i
y x ii
? ? ?
? ? ?
 
From (ii), we get 
23 yx ?? 
Substituting 23 yx ?? in (i) we get 
? ? 3 7 2 3 10 0
3 14 21 10 0
11 11
11
1
11
xx
xx
x
x
? ? ? ?
? ? ? ? ?
? ? ?
? ? ? ?
?
 
Putting 1 x ?? in 2 3, yx ?? we get 
? ? 2 1 3
23
1
1
y
y
? ? ? ? ?
? ? ?
?
??
 
Hence, the solution of the given system of equations is 1, 1. xy ? ? ? 
 
3. 0.4x + 0.3y = 1.7 
0.7x + 0.2y = 0.8 
Sol: 
 
 
 
The given system of equation is 
? ?
? ?
0.4 0.3 1.7 ...
0.7 0.2 0.8 ...
x y i
x y ii
??
??
 
Multiplying both sides of (i) and (ii), by 10, we get 
? ?
? ?
4 3 17 ...
7 2 8 ...
x y iii
x y iv
??
??
 
From (iv), we get 
7 8 2
82
7
7
xy
y
x
??
?
?
 
Substituting 
82
7
y
x
?
? in (iii), we get 
82
4 3 17
7
32 8
3 17
7
32 29 17 7
y
y
y
y
y
? ??
??
??
??
?
? ? ?
? ? ? ?
 
29 119 32
29 87
87
3
29
y
y
y
? ? ?
??
? ? ?
 
Putting 3 y ? in 
82
,
7
y
x
?
? we get 
8 2 3
7
x
??
? 
86
7
14
7
2
?
?
?
?
 
Hence, the solution of the given system of equation is 2, 3. xy ?? 
 
4. 0.8
2
x
y ?? 
Sol: 
0.8
2
x
y ?? 
 
And 
7
10
2
y
x
?
?
 
72
2 1.6 10
2
x y and
xy
?
? ? ? ?
?
 
2 1.6 7 10 5 x y and x y ? ? ? ? 
Multiply first equation by 10 
10 20 16 10 5 7 x y and x y ? ? ? ? 
Subtracting the two equations 
15 9
93
15 5
3 6 2
1.6 2 1.6
5 5 5
y
y
x
?
??
??
? ? ? ? ?
??
??
 
Solution is 
23
,
55
??
??
??
 
 
 
 
5. 7(y + 3) – 2 (x + 3) = 14 
4(y – 2) + 3 (x – 3) = 2 
Sol: 
The given system of equations id 
? ? ? ? ? ?
? ? ? ? ? ?
7 3 2 3 14 ...
4 2 3 3 2 ...
y x i
y x ii
? ? ? ?
? ? ? ?
 
From (i), we get 
7 21 2 4 14
7 14 4 21 2
23
7
xx
yx
x
y
? ? ? ?
? ? ? ? ?
?
??
 
From (ii), we get 
4 8 3 9 2 yx ? ? ? ? 
? ?
4 3 17 2 0
4 3 19 0 ...
yx
y x iii
? ? ? ? ?
? ? ? ?
 
Substituting 
23
7
x
y
?
? in (iii), we get 
Page 5


 
 
 
 
 
               Exercise 3.3 
Solve the following systems of equations: 
1. 11x + 15y + 23 = 0 
7x – 2y – 20 = 0 
Sol: 
The given system of equation is 
? ?
? ?
11 15 23 0 ...
7 2 20 0 ...
x y i
x y ii
? ? ?
? ? ?
 
From (ii), we get 
2 7 20
7 20
2
yx
x
y
??
?
??
 
Substituting 
7 20
2
x
y
?
? in (i) we get 
7 20
11 15 23 0
2
105 300
11 23 0
2
22 105 300 46
0
2
127 254 0
127 254
254
2
127
x
x
x
x
xx
x
x
x
? ??
? ? ?
??
??
?
? ? ? ?
? ? ?
??
? ? ?
??
? ? ?
 
 
Putting 2 x ? in 
7 20
2
x
y
?
? we get 
7 2 20
2
14 20
2
6
2
3
y
??
??
?
?
?
?
??
 
Hence, the solution of the given system of equations is 2, 3. xy ? ? ? 
 
 
 
2. 3x – 7y + 10 = 0 
y – 2x – 3 = 0 
Sol: 
The given system of equation is 
? ?
? ?
3 7 10 0 ...
2 3 0 ...
x y i
y x ii
? ? ?
? ? ?
 
From (ii), we get 
23 yx ?? 
Substituting 23 yx ?? in (i) we get 
? ? 3 7 2 3 10 0
3 14 21 10 0
11 11
11
1
11
xx
xx
x
x
? ? ? ?
? ? ? ? ?
? ? ?
? ? ? ?
?
 
Putting 1 x ?? in 2 3, yx ?? we get 
? ? 2 1 3
23
1
1
y
y
? ? ? ? ?
? ? ?
?
??
 
Hence, the solution of the given system of equations is 1, 1. xy ? ? ? 
 
3. 0.4x + 0.3y = 1.7 
0.7x + 0.2y = 0.8 
Sol: 
 
 
 
The given system of equation is 
? ?
? ?
0.4 0.3 1.7 ...
0.7 0.2 0.8 ...
x y i
x y ii
??
??
 
Multiplying both sides of (i) and (ii), by 10, we get 
? ?
? ?
4 3 17 ...
7 2 8 ...
x y iii
x y iv
??
??
 
From (iv), we get 
7 8 2
82
7
7
xy
y
x
??
?
?
 
Substituting 
82
7
y
x
?
? in (iii), we get 
82
4 3 17
7
32 8
3 17
7
32 29 17 7
y
y
y
y
y
? ??
??
??
??
?
? ? ?
? ? ? ?
 
29 119 32
29 87
87
3
29
y
y
y
? ? ?
??
? ? ?
 
Putting 3 y ? in 
82
,
7
y
x
?
? we get 
8 2 3
7
x
??
? 
86
7
14
7
2
?
?
?
?
 
Hence, the solution of the given system of equation is 2, 3. xy ?? 
 
4. 0.8
2
x
y ?? 
Sol: 
0.8
2
x
y ?? 
 
And 
7
10
2
y
x
?
?
 
72
2 1.6 10
2
x y and
xy
?
? ? ? ?
?
 
2 1.6 7 10 5 x y and x y ? ? ? ? 
Multiply first equation by 10 
10 20 16 10 5 7 x y and x y ? ? ? ? 
Subtracting the two equations 
15 9
93
15 5
3 6 2
1.6 2 1.6
5 5 5
y
y
x
?
??
??
? ? ? ? ?
??
??
 
Solution is 
23
,
55
??
??
??
 
 
 
 
5. 7(y + 3) – 2 (x + 3) = 14 
4(y – 2) + 3 (x – 3) = 2 
Sol: 
The given system of equations id 
? ? ? ? ? ?
? ? ? ? ? ?
7 3 2 3 14 ...
4 2 3 3 2 ...
y x i
y x ii
? ? ? ?
? ? ? ?
 
From (i), we get 
7 21 2 4 14
7 14 4 21 2
23
7
xx
yx
x
y
? ? ? ?
? ? ? ? ?
?
??
 
From (ii), we get 
4 8 3 9 2 yx ? ? ? ? 
? ?
4 3 17 2 0
4 3 19 0 ...
yx
y x iii
? ? ? ? ?
? ? ? ?
 
Substituting 
23
7
x
y
?
? in (iii), we get 
 
23
4 3 19 0
7
8 12
3 19 0
7
8 12 21 133 0
29 145 0
29 145
145
5
29
x
x
x
x
xx
x
x
x
? ??
? ? ?
??
??
?
? ? ? ?
? ? ? ? ?
? ? ?
??
? ? ?
 
Putting 5 x ? in 
23
,
7
x
y
?
? we get 
2 5 7
7
y
??
? 
10 3
7
7
7
1
1 y
?
?
?
?
??
 
Hence, the solution of the given system of equations is 5, 1. xy ?? 
 
6. 
?? 7
+
?? 3
= 5 
?? 2
-
?? 9
= 6  
Sol: 
The given system of equation is 
? ?
? ?
5 ...
73
6 ...
29
xy
i
xy
ii
??
??
 
From (i), we get 
37
5
21
3 7 105
3 105 7
105 7
3
xy
xy
xy
y
x
?
?
? ? ?
? ? ?
?
??
 
From (ii), we get 
Read More
126 videos|457 docs|75 tests

Top Courses for Class 10

FAQs on Pair of Linear Equations in Two Variables - 3 RD Sharma Solutions - Mathematics (Maths) Class 10

1. What is the definition of a pair of linear equations in two variables?
Ans. A pair of linear equations in two variables is a set of two equations that involve two variables and are of degree one. The general form of such equations is ax + by = c, where a, b, and c are constants.
2. How can I solve a pair of linear equations in two variables?
Ans. There are several methods to solve a pair of linear equations in two variables, such as the substitution method, elimination method, and graphical method. The choice of method depends on the given equations and personal preference.
3. Is it always possible to find a solution for a pair of linear equations in two variables?
Ans. Not always. If the given pair of equations represents parallel lines, there will be no solution as parallel lines do not intersect. Similarly, if the equations represent the same line, there will be infinitely many solutions.
4. What is the importance of solving a pair of linear equations in two variables?
Ans. Solving a pair of linear equations in two variables helps in finding the common solution(s) of the equations. These solutions can be used to determine the values of the variables in real-life situations, such as finding the intersection point of two lines or solving problems related to cost and revenue.
5. Can a pair of linear equations in two variables have more than one solution?
Ans. Yes, a pair of linear equations in two variables can have infinitely many solutions. This happens when the equations represent the same line. In such cases, any point on the line will satisfy both equations, resulting in infinitely many solutions.
126 videos|457 docs|75 tests
Download as PDF
Explore Courses for Class 10 exam

Top Courses for Class 10

Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Related Searches

Extra Questions

,

Pair of Linear Equations in Two Variables - 3 RD Sharma Solutions | Mathematics (Maths) Class 10

,

past year papers

,

Sample Paper

,

shortcuts and tricks

,

Exam

,

Pair of Linear Equations in Two Variables - 3 RD Sharma Solutions | Mathematics (Maths) Class 10

,

Viva Questions

,

video lectures

,

Objective type Questions

,

Semester Notes

,

Previous Year Questions with Solutions

,

Free

,

Pair of Linear Equations in Two Variables - 3 RD Sharma Solutions | Mathematics (Maths) Class 10

,

study material

,

Summary

,

Important questions

,

ppt

,

mock tests for examination

,

practice quizzes

,

pdf

,

MCQs

;