NDA & NA Exam (II)- 2023 - Mathematics Defence Question Paper

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NDA & NA Exam (II)- 2023 - Mathematics

NDA & NA Exam (II)- 2023 - Mathematics Defence Questions

1.
If \( z\bar{z} = |z + \bar{z}| \), where \( z = x + iy \), \( i = \sqrt{-1} \), then the locus of \( z \) is a pair of:
A.
straight lines
B.
rectangular hyperbolas
C.
parabolas
D.
circles
ANSWER :
D. circles
2.
If \( 1! + 3! + 5! + 7! + \ldots + 199! \) is divided by 24, what is the remainder?
A.
3
B.
6
C.
7
D.
9
ANSWER :
C. 7
3.
What is the value of \( \sqrt{12 + 5i} + \sqrt{12 - 5i} \), where \( i = \sqrt{-1} \)?
A.
24
B.
25
C.
\( 5\sqrt{2} \)
D.
\( 5(\sqrt{2} - 1) \)
ANSWER :
C. \( 5\sqrt{2} \)
4.
If \( A = \begin{bmatrix} 1 \\ 2 \\ 3 \end{bmatrix} \), then what is the value of \( \det(I + AA') \), where \( I \) is the \( 3 \times 3 \) identity matrix?
A.
15
B.
6
C.
0
D.
−1
ANSWER :
A. 15
5.
If A, B and C are square matrices of order 3 and \( \det(BC) = 2\det(A) \), then what is the value of \( \det(2A^{-1}BC) \)?
A.
16
B.
128
C.
4
D.
2
ANSWER :
A. 16
6.
If the \( n \)th term of a sequence is \( \frac{2n + 5}{7} \), then what is the sum of its first 140 terms?
A.
2840
B.
2780
C.
2920
D.
5700
ANSWER :
C. 2920
7.
Let A be a skew-symmetric matrix of order 3. What is the value of \( \det(4A^{4}) - \det(3A^{3}) + \det(2A^{2}) - \det(A) + \det(-I) \), where I is the identity matrix of order 3?
A.
−1
B.
0
C.
1
D.
2
ANSWER :
A. −1
8.
If
\( A = \begin{bmatrix} 0 & 3 & 4 \\ -3 & 0 & 5 \\ -4 & -5 & 0 \end{bmatrix} \)
then which one of the following statements is correct?
A.
\( A^{2} \) is symmetric matrix with \( \det(A^{2}) = 0 \).
B.
\( A^{2} \) is symmetric matrix with \( \det(A^{2}) \neq 0 \).
C.
\( A^{2} \) is skew-symmetric matrix with \( \det(A^{2}) = 0 \).
D.
\( A^{2} \) is skew-symmetric matrix with \( \det(A^{2}) \neq 0 \).
ANSWER :
A. \( A^{2} \) is symmetric matrix with \( \det(A^{2}) = 0 \).
9.
If
\( A = \begin{bmatrix} 2 & 0 & 0 \\ 0 & 3 & 0 \\ 0 & 0 & 4 \end{bmatrix} \)
then which of the following statements are correct?
1. \( A^{n} \) will always be singular for any positive integer \( n \).
2. \( A^{n} \) will always be a diagonal matrix for any positive integer \( n \).
3. \( A^{n} \) will always be a symmetric matrix for any positive integer \( n \).
Select the correct answer using the code given below:
A.
1 and 2 only
B.
2 and 3 only
C.
1 and 3 only
D.
1, 2 and 3
ANSWER :
B. 2 and 3 only
10.
If \( (a + b), 2b, (b + c) \) are in HP, then which one of the following is correct?
A.
\( a, b \) and \( c \) are in AP
B.
\( a - b, b - c \) and \( c - a \) are in AP
C.
\( a, b \) and \( c \) are in GP
D.
\( a - b, b - c \) and \( c - a \) are in GP
ANSWER :
C. \( a, b \) and \( c \) are in GP