pair-of-linear-equations-in-two-variablesWHERE cd.courseId=9 AND cd.subId=6 AND chapterSlug='pair-of-linear-equations-in-two-variables' and status=1SELECT ex_no,page_number,question,question_no,id,chapter,solution FROM question_mgmt as q WHERE courseId='9' AND subId='6' AND chapterId='270' AND ex_no!=0 AND status=1 ORDER BY ex_no,CAST(question_no AS UNSIGNED)
At Saralstudy, we are providing you with the solution of Class 10 Mathematics Pair of Linear Equations in Two Variables according to the latest NCERT (CBSE) Book guidelines prepared by expert teachers. Here we are trying to give you a detailed answer to the questions of the entire topic of this chapter so that you can get more marks in your examinations by preparing the answers based on this lesson. We are trying our best to give you detailed answers to all the questions of all the topics of Class 10 Mathematics Pair of Linear Equations in Two Variables so that you can prepare for the exam according to your own pace and your speed.
Let the present age of Aftab and his father be x years and y years respectively.
According to question,
7 years ago, we have
x – 7 = 7 (y - 7)
Or, x – 7 = 7y – 49
Or, x – 7y = - 42 …………… (1)
3 years from now, we have
(x + 3) = 3 (y + 3)
Or, x + 3 = 3y + 9
Or, x – 3y = 6 ……………. (2)
Graphical Representation
From equation (1), x – 7y = -42
Table value of x and y
x: |
0 |
-42 |
-35 |
y: |
6 |
0 |
1 |
From equation (2), x – 3y = 6
Table value of x and y
x: |
0 |
9 |
6 |
y: |
-2 |
1 |
0 |
Plotting the tables on the graph:
Exercise 1 ( Page No. : 44 )
Let the cost of one bat and one ball be x Rupees and y Rupees respectively.
According to first condition,
3x + 6y = ₨ 3900 …………….(1)
According to second condition,
x + 3y = ₨ 1300 …………….(2)
Graphical Representation
From equation (1), 3x + 6y = 3900
Table value of x and y
x: |
100 |
300 |
700 |
y: |
600 |
500 |
300 |
From equation (2), x + 3y = 1300
Table value of x and y
x: |
100 |
700 |
400 |
y: |
400 |
200 |
300 |
1 Unit = 100
Exercise 1 ( Page No. : 44 )
Let the cost of one kg apple be x ₨ and 1 kg grapes be y ₨.
According to first condition,
2x + y = 160 ₨ …………..(1)
According to second condition,
4x + 2y = 300
2x + y = 150 ……………….(2)
Graphical Representation
Table for equation (1), 2x + y = 160
Table value of x and y
x: |
40 |
60 |
80 |
y: |
60 |
40 |
0 |
Table for equation (2), 2x + y = 150
Table value of x and y
x: |
40 |
60 |
20 |
y: |
70 |
30 |
110 |
Exercise 2 ( Page No. : 50 )
Given equations,
x + y + 1 = 0 …………………. (1)
3x + 2y + 2 = 0 ………………….. (2)
From the equation (1), we get
x |
0 |
1 |
2 |
y |
1 |
2 |
3 |
From the equation (2), we get
x |
4 |
3 |
0 |
y |
0 |
3 |
6 |
The coordinates of vertices of triangle formed by these lines and the x- axis are (-1, 0), (4, 0), (2, 3).
(i) x + y = 14 …………….(1)
x – y = 4 …………….(2)
From the equation (1), we get
x = 14 - y …………….(3)
Putting the value of x in equation (2), we get
(14 - y) – y = 4
14 – y – y = 4
- 2y = - 10
Putting the value of y in equation (3),
x = 14 – 5
x = 9
Hence, x = 9 and y = 5
(iii) 3x - y = 3 …………….(1)
9x – 3y = 9…………….(2)
From the equation (1), we get
Putting the value of y in equation (2), we get
9x – 3 (3x - 3) = 9
9x – 9x + 9 = 9
9 = 9, which is true.
Therefore, pair of linear equation has infinite many solutions.
Exercise 3 ( Page No. : 53 )
(i) Let the numbers be x and y, such that x > y
Therefore, according to question
x - y = 26 …………….(1)
x = 3y…………….(2)
Putting the value of x from equation (2) to equation (1), we get
3y – y = 26
2y = 26
y = 13
Putting the value in equation (2), we get
x = 3 x 13
x = 39
Hence, the numbers are 39 and 13.
(ii) Let one be x◦ and other be y◦ such that (x◦ > y◦)
Therefore, according to question
x◦ + y◦ = 180◦…………….(1) (Supplementary angles)
x◦ = 18 + y◦…………….(2)
Putting the value of x from equation (2) to equation (1), we get
18 + y◦ + y◦ = 180◦
2y◦ = 162◦
Putting the value of y in equation (2), we get
x◦ = 18 + 81
x = 99
(iv) Let the fixed charge be = ₨ x
Let the charge for 1 km distance be = ₨ y
According to first condition,
x + 10y = ₨ 105
x = 105 – 10y …………….(1)
According to second condition,
x + 15y = 155 ………………(2)
Putting the value of x in equation (2), we get
105 – 10y + 15y = 155
5y = 50
y = 10
Putting the value of y in equation (2), we get
x + 15 x 10 = 155
x = 5
Hence, the fixed charge for taxi is ₨ 5 and, the charge for one km distance is ₨ 50.
Charge for 25 km distance
= 25 x 10 + 5
= ₨ 255
(vi) Let the age of Jacob be = x years
Let the age of Jacob’s father be = y years
After 5 years,
Jacob’s age x + 5 years
Son’s age y + 5 years
According to question,
x + 5 = 3 (y + 5)
x + 5 = 3y + 15
x = 3y + 10………………(1)
Five years ago,
(x- 5) = 7 (y - 5)
x – 5 = 7y – 35
x – 7y = -30……………….(2)
Putting the value of x in equation (2), we get
3y + 10 - 7y = -30
-4y = -40
y = 10
Putting the value of y in equation (1), we get
x = 3 (10) + 10
x = 40
Hence, the present age of Jacob is 40 years and the age of his son is 10 years.