NDA & NA Exam (II)- 2018 - Mathematics Defence Question Paper

NDA Previous Year Question Papers Question Papers
NDA & NA Exam (II)- 2018 - Mathematics

NDA & NA Exam (II)- 2018 - Mathematics Defence Questions

21.
The system of equations \( 2x + y - 3z = 5 \), \( 3x - 2y + 2z = 5 \) and \( 5x - 3y - z = 16 \)
A.
is inconsistent
B.
is consistent, with a unique solution
C.
is consistent, with infinitely many solutions
D.
has its solution lying along x-axis in three-dimensional space
ANSWER :
B. is consistent, with a unique solution
22.
Which one of the following is correct in respect of the cube roots of unity?
A.
They are collinear
B.
They lie on a circle of radius \( \sqrt{3} \)
C.
They form an equilateral triangle
D.
None of the above
ANSWER :
C. They form an equilateral triangle
23.
If u, v and w (all positive) are the pth, qth and rth terms of a GP, then the determinant of the matrix \( \begin{bmatrix} \ln u & p & 1 \\ \ln v & q & 1 \\ \ln w & r & 1 \end{bmatrix} \) is
A.
0
B.
1
C.
(p − q)(q − r)(r − p)
D.
ln u × ln v × ln w
ANSWER :
A. 0
24.
Let the coefficient of the middle term of the binomial expansion of \( (1 + x)^{2n} \) be \( \alpha \) and those of two middle terms of the binomial expansion of \( (1 + x)^{2n-1} \) be \( \beta \) and \( \gamma \). Which one of the following relations is correct?
A.
\( \alpha > \beta + \gamma \)
B.
\( \alpha < \beta + \gamma \)
C.
\( \alpha = \beta + \gamma \)
D.
\( \alpha = \beta\gamma \)
ANSWER :
C. \( \alpha = \beta + \gamma \)
25.
Let \( A = \{x \in R : -1 \leq x \leq 1\} \), \( B = \{y \in R : -1 \leq y \leq 1\} \) and S be the subset of \( A \times B \), defined by \( S = \{(x, y) \in A \times B : x^{2} + y^{2} = 1\} \). Which one of the following is correct?
A.
S is a one-one function from A into B
B.
S is a many-one function from A into B
C.
S is a bijective mapping from A into B
D.
S is not a function
ANSWER :
D. S is not a function
26.
Let \( T_{r} \) be the \( r^{th} \) term of an AP for r = 1, 2, 3, .... If for some distinct positive integers m and n we have \( T_{m} = \frac{1}{n} \) and \( T_{n} = \frac{1}{m} \), then what is \( T_{mn} \) equal to?
A.
\( (mn)^{-1} \)
B.
\( m^{-1} + n^{-1} \)
C.
1
D.
0
ANSWER :
C. 1
27.
Suppose f(x) is such a quadratic expression that it is positive for all real x. If \( g(x) = f(x) + f'(x) + f''(x) \), then for any real x
A.
g(x) < 0
B.
g(x) > 0
C.
g(x) = 0
D.
\( g(x) \leq 0 \)
ANSWER :
B. g(x) > 0
28.
Consider the following in respect of matrices A, B and C of same order:
1. \( (A + B + C)' = A' + B' + C' \)
2. \( (AB)' = A'B' \)
3. \( (ABC)' = C'B'A' \)
where A′ is the transpose of the matrix A.
Which of the above are correct?
A.
1 and 2 only
B.
2 and 3 only
C.
1 and 3 only
D.
1, 2 and 3
ANSWER :
C. 1 and 3 only
29.
The sum of the binary numbers \( (11011)_{2} \), \( (10110110)_{2} \) and \( (10011x0y)_{2} \) is the binary number \( (101101101)_{2} \). What are the values of x and y?
A.
x = 1, y = 1
B.
x = 1, y = 0
C.
x = 0, y = 1
D.
x = 0, y = 0
ANSWER :
B. x = 1, y = 0
30.
Let matrix B be the adjoint of a square matrix A, I be the identity matrix of same order as A. If k (≠ 0) is the determinant of the matrix A, then what is AB equal to?
A.
I
B.
kI
C.
\( k^{2}I \)
D.
\( \frac{1}{k}I \)
ANSWER :
B. kI