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NDA II 2022 Mathematics Test - 5
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NDA II 2022 Mathematics Test - 5
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  • Question 1/10
    2.5 / -0.83

    What is the value of x, y and z in the following?

    Solutions

    For x,

    2x+6 = 0

    ⇒ 2x = -6

    ⇒ X = -6/2

    ⇒ X = -3

    For y,

    4y -14 = 6y-4

    ⇒ 4y-6y = -4 +14

    ⇒ -2y = 10

    ⇒ Y = 10/(-2)

    ⇒ Y = -5

    For z,

    2z+8 = 12

    ⇒ 2z = 12-8

    ⇒ 2z = 4

    ⇒ Z = 2

     

  • Question 2/10
    2.5 / -0.83

    Find the value of the following matrix:

    Solutions

    Using elementary operations on a matrix;

    ⇒ Expanding along R2, gives both determinant values as 0.

     

  • Question 3/10
    2.5 / -0.83

    Find the value of |A|.

    Solutions

    = 10(3*13-0) – 17(0) + 1(0-3)

    = 10(39) – 0 -3

    =390-3

    =387

     

  • Question 4/10
    2.5 / -0.83

    Find the determinant of the following

    Solutions

    Determinant of A

    = 3(12*3 -0*4) – 8((-3*3) – 12*0) + 4((-3*4) – 12*12)

    = 3(12) -8(-9) + 4( -12-144)

    = 3*36 + 72 + 4*(-156)

    = 108 + 72 – 624

    = -444

     

  • Question 5/10
    2.5 / -0.83

    If A is square matrix of order 4x4, then |kA| is

    Solutions

    For a square matrix A, the determinant of matrix is, when all the elements are multiplied by a constant k, becomes, kn|A|

     

  • Question 6/10
    2.5 / -0.83

    Find the Minor of the following:

    Solutions

    M22 = (1*9)-(7*3) = 9-21 = -12

     

  • Question 7/10
    2.5 / -0.83

    Which of the following is the A22 cofactor for the given matrix?

    Solutions

    Cofactor of A22 = (4*(-14)) – (5*2) = -56 - 10 = -66

     

  • Question 8/10
    2.5 / -0.83

    Points A(7, 10), B(-2, 5) and C(3, -4) are the vertices of

    Solutions

    AB=BC

    Therefore, Δ ABC is an isosceles triangle .....(3)

    Also, AB2 = 106 units .....(4)

    BC2 = 106 units .....(5)

    AC2 = 212 units .....(6)

    From equations 4, 5 and 6, we have

    AB2 + BC2 = AC2

    So, it satisfies the Pythagoras theorem.

    Δ ABC is right angled triangle .....(7)

    From 3 and 7, we have

    Δ ABC is an isosceles right angled triangle.

     

  • Question 9/10
    2.5 / -0.83

    Find the equation of the ellipse which passes through the point (4, 1) and having its foci at (±3, 0).

    Solutions

    Let the equation of the required ellipse be

    Coordinates of foci = (±3, 0) ...(ii)

    We know that,

    Coordinates of foci = (±c, 0) ...(iii)

    ∴ From eq. (ii) and (iii), we get

    c = 3

    We know that,

    C2 = a2 – b2

    ⇒ (3)2= a2 – b2

    ⇒ 9 = a2– b2

    ⇒ b2= a2 – 9 ...(iv)

    Given that ellipse passing through the points (4, 1)

    So, point (4, 1) will satisfy the eq. (i)

    Taking point (4, 1) where x = 4 and y = 1

    Putting the values in eq. (i), we get

    16a2– 144 + a2 = a2(a2 – 9)

    ⇒ 17a2 – 144 = a4 – 9a2

    ⇒ a4– 9a2 – 17a2 + 144 = 0

    ⇒ a4 – 26a2 + 144 = 0

    ⇒ a4 – 8a2 – 18a2 + 144 = 0

    ⇒ a2(a2 – 8) – 18(a2 – 8) = 0

    ⇒ (a2 – 8)(a2 – 18) = 0

    ⇒ a2 – 8 = 0 or a2 – 18 = 0

    ⇒ a2 = 8 or a2 = 18

    If a2 = 8 then

    b2= 8– 9=- 1

    Since the square of a real number cannot be negative. So, this is not possible

    If a2 = 18 then

    b2 = 18 – 9= 9

    So, equation of ellipse if a2 = 18 and b2 = 9

     

  • Question 10/10
    2.5 / -0.83

    Find the distance between the parallel planes 2x+3y+4z=1 and 4x+6y+8z=12

    Solutions

    Equation of the planes 2x+3y+4z=1 and 4x+6y+8z=12 or 2x+3y+4z = 6

    We know that distance between ax+by+cz+d1=0 and ax+by+cz+d1=0 is

     

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