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10th Grade > Mathematics

PAIR OF LINEAR EQUATIONS IN TWO VARIABLES MCQs

Total Questions : 30 | Page 2 of 3 pages
Question 11.


If 3x=2y2 is written in the standard form ax+by+c=0, what will be the possible values of a, b and c?
 


  1.     a = 1, b = -2 and c = 2
  2.     a = 3, b = -2 and c = 2
  3.     a = -3, b = -2 and c = 1
  4.     a = -3, b = 2 and c = -2
 Discuss Question
Answer: Option B. -> a = 3, b = -2 and c = 2
:
B and D

The given equation is
3x=2y2.
After rearranging the equation, we get
3x2y+2=0
On comparing the above equation with ax+by+c=0, we get
a = 3, b = -2 and c = 2
The values of a, b and c are 3, -2 and 2 respectively.
But the equation can also be written as
(1)×(3x2y+2)=(1)×0
3x+2y2=0
On comparing the above equation with ax+by+c=0, we get
a = -3, b = 2 and c = -2
The values of a, b and c are -3, +2 and -2 respectively.
Hence, we have two sets of values for a, b and c.


Question 12.


The line represented by the equation 4x+5y=10 intersects the y axis at (0, 2).


  1.     True
  2.     False
  3.     a = -3, b = -2 and c = 1
  4.     a = -3, b = 2 and c = -2
 Discuss Question
Answer: Option A. -> True
:
A

The line intersects the y axis when the value of x coordinate is 0.
Thus, on y axis, x=0.
Substituting this value in the given equation:
5y=10
y=2
Thus, the line intersects the y axis at point (0,2).


Question 13.


54 is divided into two parts such that sum of 10 times the first part and 22 times the second part is 780. What is the bigger part?


  1.     34
  2.     32
  3.     30
  4.     24
 Discuss Question
Answer: Option A. -> 34
:
A

Let the 2 parts of 54 be x and y


 x+y = 54 ....(i)


and 10x + 22y = 780 ...(ii)


Multiply (i) by 10 , we get 


10 x + 10 y = 540 ...(iii)


 Subtracting  (ii) from (iii)


 - 12y = - 240


    y  =  20


Subsituting y = 20 in x + y = 54 ,
x + 20 = 54
x = 34 


Hence, x = 34 and y = 20


Question 14.


Measure of one of the angles of a parallelogram is twice the measure of its adjacent angle. Then angles of the parallelogram are


  1.     6010018020
  2.     1402012080
  3.     6012060120
  4.     100, 8010080 
 Discuss Question
Answer: Option C. -> 6012060120
:
C
Let the measure of the angle be x and that of its adjacent angle be y.
x=2y ...(i)  (given)
x+y=180 ...(ii)
(sum of adjacent angles of a parallelogram is 180)
On substituting (i) in (ii), we get
2y+y=180
y=60 
Since x=2yx=120.
We know that opposite angles of parallelogram are equal.
Measure of the angles are 6012060 and 120.
Question 15.


The lines that represent these two equations x+2y=5 and 4x+4y6=0 meet at only one point (-2, 3.5). The pair of equations is


  1.     dependent
  2.     consistent
  3.     inconsistent
  4.     (a) and (b) above.
 Discuss Question
Answer: Option B. -> consistent
:
B

A pair of linear equations in two variables which has a solution, is said to be consistent.
Here the lines representing the given linear equations are meeting only at point (-2, 3.5) giving a unique solution. Therefore, it is a consistent pair of linear equations.
Now, a pair of linear equations in two variables is said to be dependent when the lines representing them are coinciding i.e. will have many solutions.
Here, the lines have only one solution (-2, 3.5). Therefore, they aren't dependent.


Question 16.


Solving 52+x+1y4=262+x3y4=1,
we get


x = ___
y = ___


 Discuss Question
Answer: Option B. -> consistent
:

Let, p = 12+x and  q = 1y4
Thus, given equations reduce to,
5p+q=2  ... (i)
6p3q=1   ... (ii)
On multiplying (i) by 3 and then adding it to (ii), we get


15p+3q=6
6p3q=1


_______________


   21p=7 
p=13 
and  on substituting this value in (ii) we get
6133q=1
q=13
Now, p=12+x  
13=12+x 
x=1
We know that q=1y4
13=1y4 
y=7


Question 17.


Find the point at which the line represented by the equation 6x+5y=9, intersects the x-axis. 


  1.     (0,32)
  2.      (32,0)
  3.     (1,0)
  4.     (2,3)
 Discuss Question
Answer: Option B. ->  (32,0)
:
B

Let the line intersects at point (x, y).
We know that if a line intersects the x-axis then the  y coordinate of the point at which it intersects will be 0.
y = 0
On substituting y = 0 in the given equation, we get
6x+0=9
x=32
Thus, the point at which the given line intersects the x-axis is (32,0).


Question 18.


For the given linear equation y3x+1=0, what are the values of y if x=[3,4,2]


  1.     5, -8, 13
  2.     8, 5, 13
  3.     8, 8, 8
  4.     8, -13, 5
 Discuss Question
Answer: Option D. -> 8, -13, 5
:
D

We have y3x+1=0
For x=3
y3(3)+1=0
y=8
For x=4
y3(4)+1=0
y=13
For x=2
y3(2)+1=0
y=5
Thus, the values of y if x=[3,4,2]  are 8, -13 and 5 respectively.


Question 19.


Which of the following are Pair of Linear Equation in two variables?


  1.     2x+y=2;3xz=2
  2.     12x+4y+3=0;4x+4y+4=0
  3.     x+2=0;a+2b=0
  4.     x+y3=0;4a+2b+c=24
 Discuss Question
Answer: Option B. -> 12x+4y+3=0;4x+4y+4=0
:
B

Two linear equations in same two variables are called pair of linear equation in two variables.


12x+4y+3=0 and 4x+4y+4=0
are linear equations in same two variables.


Question 20.


If the linear equation y=7x4 is written in standard form, the standard form being ax+by+c=0, then what are the possible value of a,b,c?


  1.     a=7,b=1,c=4
  2.     a=7,b=1,c=4
  3.     a=7,b=1,c=4
  4.     none of these
 Discuss Question
Answer: Option A. -> a=7,b=1,c=4
:
A

The standard form of a linear equation is ax+by+c=0.
The given equation is y=7x4.
It can be rewritten as 7x+y+4=0.
a=7,b=1 and c=4.
But the equation can also be written as,
7xy4=0.
a=+7,b=1 and c=4.
 


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