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NCERT Solutions for Class 10th Maths:Linear Equations Exercise 3.2




In this page we have NCERT Solutions for Class 10th Maths:Linear Equations for Exercise 3.2. Hope you like them and do not forget to like , social_share and comment at the end of the page.
Question 1
Form the pair of linear equations in the following problems, and find their solutions graphically.

(i) 10 students of Class X took part in a Mathematics quiz. If the number of girls is 4 more than the number of boys, find the number of boys and girls who took part in the quiz.
(ii) 5 pencils and 7 pens together cost Rs 50, whereas 7 pencils and 5 pens together cost Rs 46. Find the cost of one pencil and that of one pen.

Solution
i) Let number of boys = x
Number of girls = y
Given that total number of student is 10 so that
= 10
or
= 10 – x
Putting = 10, 0 we get
 
x
10
0
y
0
10

Given that If the number of girls is 4 more than the number of boys
So that
+ 4
Putting x = -4, 0 and we get
 
x
-4
0
y
0
4

Graphical representation

Therefore, number of boys = 3 and number of girls = 7.
ii) Let cost of pencil = Rs x
Cost of pens = Rs y
5 pencils and 7 pens together cost Rs 50,
So we get
5x + 7y = 50
or
y = (50 - 5 x) /7
Here putting x=0, will give fractional value of y which will be difficult to drawn in graph, so we take values such that, we get integers values
Putting value of x = 3 and -4 we get
 
 
x
3
-4
y
5
10

Given that 7 pencils and 5 pens together cost Rs 46
7x + 5y = 46
y = (46 - 7x)/5

Putting x = -2, 3 we get
 
x
-2
3
y
12
5

Graphical representation

Therefore, cost of one pencil = Rs 3 and cost of one pen = Rs 5.
Question 2
On comparing the ratios a1/a2b1/b2 and c1/c2, find out whether the lines representing the following pairs of linear equations intersect at a point, are parallel or coincident.
(i) 5x – 4y + 8 = 0
7x + 6y – 9 = 0
(ii) 9x + 3y + 12 = 0
18x + 6y + 24 = 0
 
(iii) 6x – 3y + 10 = 0
2x – y + 9 = 0
 
Answer
i) Comparing these equation with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get
a1 = 5, b1 = -4, and c1 = 8
a2 =7, b2 = 6 and c2 = -9
a1/a2 = 5/7,
b1/b2 = -4/6 and
c1/c2 = 8/-9
Hence, a1/a2 ≠ b1/b2
Therefore, both are intersecting lines at one point.
ii)Comparing these equations with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get
a1 = 9, b1 = 3, and c1 = 12
a2 = 18, b2 = 6 and c2 = 24
a1/a2 = 9/18 = 1/2
b1/b2 = 3/6 = 1/2 and
c1/c2 = 12/24 = 1/2
Hence, a1/a2 = b1/b=c1/c2

Therefore, both lines are coincident
iii) Comparing these equations with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get
a1 = 6, b1 = -3, and c1 = 10
a2 = 2, b2 = -1 and c2 = 9
a1/a2 = 6/2 = 3/1
b1/b2 = -3/-1 = 3/1 and
c1/c2 = 12/24 = 1/2
Hence, a1/a2 = b1/bc1/c2

Therefore, both lines are parallel

Question 3
On comparing the ratios a1/a2b1/b2 and c1/c2 find out whether the following pair of linear equations are consistent, or inconsistent.
(i) 3x + 2y = 5; 2x – 3y = 7
(ii) 2x – 3y = 8; 4x – 6y = 9
(iii) 3/2x + 5/3y = 7; 9– 10y = 14
(iv) 5x – 3y = 11; – 10x + 6y = –22
(v) 4/3x + 2y =8; 2x + 3y = 12
Answer
(i) 3x + 2y = 5 ,2x – 3y = 7
Comparing these equations with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get

a1/a2 = 3/2
b1/b2 = -2/3 and
c1/c2 = 5/7
Hence, a1/a2 ≠ b1/b2
These linear equations are intersecting each other at one point and thus have only one possible solution. Hence, the pair of linear equations is consistent.
(ii) 2x – 3y = 8 ,4x – 6y = 9
Comparing these equations with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get

a1/a2 = 2/4 = 1/2
b1/b2 = -3/-6 = 1/2 and
c1/c2 = 8/9
Hence, a1/a2 = b1/bc1/c2

Therefore, these linear equations are parallel to each other and thus have no possible solution. Hence, the pair of linear equations is inconsistent.

(iii) 3/2x + 5/3y = 7, 9– 10y = 14
Comparing these equations with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get

a1/a2 = 3/2/9 = 1/6
b1/b2 = 5/3/-10 = -1/6 and
c1/c2 = 7/14 = 1/2
Hence, a1/a2 ≠ b1/b2

Therefore, these linear equations are intersecting each other at one point and thus have only one possible solution. Hence, the pair of linear equations is consistent.
(iv) 5x – 3y = 11, – 10x + 6y = –22
Comparing these equations with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get

a1/a2 = 5/-10 = -1/2
b1/b2 = -3/6 = -1/2 and
c1/c2 = 11/-22 = -1/2
Hence, a1/a2 = b1/b2 =c1/c2

Therefore, these linear equations are coincident pair of lines and thus have infinite number of possible solutions. Hence, the pair of linear equations is consistent.
(v) (4/3) x + 2y =8, 2x + 3y = 12
Comparing these equations with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get

a1/a2 = 4/3/2 = 2/3
b1/b2 = /3 and
c1/c2 = 8/12 = 2/3
Hence, a1/a2 = b1/b2 =c1/c2

Therefore, these linear equations are coincident pair of lines and thus have infinite number of possible solutions. Hence, the pair of linear equations is consistent.
Question 4
Which of the following pairs of linear equations are consistent/inconsistent? If consistent, obtain the solution graphically:
(i) x + y = 5, 2x + 2y = 10
(ii) x – y = 8, 3x – 3y = 16
(iii) 2x + y – 6 = 0, 4x – 2y – 4 = 0
(iv) 2x – 2y – 2 = 0, 4x – 4y – 5 = 0
Answer
(i) x + y = 5; 2x + 2y = 10
Comparing these equations with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get

a1/a2 = 1/2
b1/b2 = 1/2 and
c1/c2 = 5/10 = 1/2
Hence, a1/a2 = b1/b2 =c1/c2
Therefore, these linear equations are coincident pair of lines and thus have infinite number of possible solutions. Hence, the pair of linear equations is consistent.
 
x + y = 5
or y = 5 - x
x
0
5
y
5
0

And, 2x + 2y = 10
or y = 5-x 
This is same as Ist equation only
x
0
5
y
5
0

Graphical representation

(ii) x – y = 8, 3x – 3y = 16
Comparing these equations with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get

a1/a2 = 1/3
b1/b2 = -1/-3 = 1/3 and
c1/c2 = 8/16 = 1/2
Hence, a1/a2 = b1/bc1/c2
Therefore, these linear equations are parallel to each other and thus have no possible solution. Hence, the pair of linear equations is inconsistent.
(iii) 2x + y – 6 = 0, 4x – 2y – 4 = 0
Comparing these equations with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get

a1/a2 = 2/4 = 1/2
b1/b2 = -1/2 and
c1/c2 = -6/-4 = 3/2
Hence, a1/a2 ≠ b1/b2

Therefore, these linear equations are intersecting each other at one point and thus have only one possible solution. Hence, the pair of linear equations is consistent.
2x + y - 6 = 0
y = 6 - 2x

 
x
0
3
y
6
0

And, 4x - 2y -4 = 0
y = 2x - 2
x
0
1
y
-2
0

Graphical representation

From the figure, it can be observed that these lines are intersecting each other at the only one point i.e., (2,2) which is the solution for the given pair of equations.
(iv) 2x – 2y – 2 = 0, 4x – 4y – 5 = 0
Comparing these equations with
a1x + b1y + c1 = 0
a2x + b2y + c2= 0
We get

a1/a2 = 2/4 = 1/2
b1/b2 = -2/-4 = 1/2 and
c1/c2 = 2/5
Hence, a1/a2 = b1/bc1/c2

Therefore, these linear equations are parallel to each other and thus, have no possible solution. Hence, the pair of linear equations is inconsistent.
Question 5
Half the perimeter of a rectangular garden, whose length is 4 m more than its width, is 36 m. Find the dimensions of the garden.
Answer
Let length of rectangle = x m
Width of the rectangle = m
According to the question,
y - x = 4 ... (i)
y + x = 36 ... (ii)
Now
y = x + 4
x
0
-4
y
4
0

y = 36 -x
x
0
36
y
36
0

Graphical representation

From the figure, it can be observed that these lines are intersecting each other at only point i.e., (16, 20). Therefore, the length and width of the given garden is 20 m and 16 m respectively.
Question 6
Given the linear equation 2x + 3y - 8 = 0, write another linear equation in two variables such that the geometrical representation of the pair so formed is:
(i) intersecting lines
(ii) parallel lines
(iii) coincident lines

Answer
(i) Intersecting lines:
For this condition,
a1/a2 ≠ b1/b2
The second line such that it is intersecting the given line is
2x + 5y - 7 = 0 as
a1/a2 = 2/2 = 1
b1/b2 = 3/5 and
a1/a2 ≠ b1/b2

(ii) Parallel lines
For this condition,
a1/a2 = b1/bc1/c2
Hence, the second line can be
6x + 9y - 8 = 0 as
a1/a2 = 2/6 = 1/3
b1/b2 = 3/9 = 1/3 and
c1/c2 = -8/-8 = 1
and a1/a2 = b1/bc1/c2

(iii) Coincident lines
For coincident lines,
a1/a2 = b1/b2 =c1/c2
Hence, the second line can be
8x + 12y  = 32 as
a1/a2 = 2/8 = 1/4
b1/b2 = 3/12 = 1/4 and
c1/c2 = -8/-24 = 1/4
and a1/a2 = b1/b2 =c1/c2

Question 7
Draw the graphs of the equations x - y + 1 = 0 and 3x + 2y - 12 = 0. Determine the coordinates of the vertices of the triangle formed by these lines and the x-axis, and shade the triangular region.
 
Answer
x - y + 1 = 0
yx + 1
x
0
-1
y
1
0

3x + 2y - 12 = 0
y = 6 – x (3/2)
x
4
0
y
0
6

Graphical representation

From the figure, it can be observed that these lines are intersecting each other at point (2, 3) and x-axis at (- 1, 0) and (4, 0). Therefore, the vertices of the triangle are (2, 3), (- 1, 0), and (4, 0).
 
 

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Reference Books for class 10

Given below are the links of some of the reference books for class 10 math.

  1. Oswaal CBSE Question Bank Class 10 Hindi B, English Communication Science, Social Science & Maths (Set of 5 Books)
  2. Mathematics for Class 10 by R D Sharma
  3. Pearson IIT Foundation Maths Class 10
  4. Secondary School Mathematics for Class 10
  5. Xam Idea Complete Course Mathematics Class 10

You can use above books for extra knowledge and practicing different questions.


Class 10 Maths Class 10 Science

Practice Question

Question 1 What is $1 - \sqrt {3}$ ?
A) Non terminating repeating
B) Non terminating non repeating
C) Terminating
D) None of the above
Question 2 The volume of the largest right circular cone that can be cut out from a cube of edge 4.2 cm is?
A) 19.4 cm3
B) 12 cm3
C) 78.6 cm3
D) 58.2 cm3
Question 3 The sum of the first three terms of an AP is 33. If the product of the first and the third term exceeds the second term by 29, the AP is ?
A) 2 ,21,11
B) 1,10,19
C) -1 ,8,17
D) 2 ,11,20






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