NDA & NA Exam (I)- 2024 - Mathematics Defence Question Paper

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NDA & NA Exam (I)- 2024 - Mathematics

NDA & NA Exam (I)- 2024 - Mathematics Defence Questions

11.
Consider the following statements in respect of two non-singular matrices A and B of the same order n:
1. \( adj(AB) = (adj A)(adj B) \)
2. \( adj(AB) = adj(BA) \)
3. \( (AB)adj(AB) - |AB|I_{n} \) is a null matrix of order n
How many of the above statements are correct?
A.
None
B.
Only one statement
C.
Only two statements
D.
All three statements
ANSWER :
B. Only one statement
12.
Consider the following statements in respect of non-singular matrix A of order n:
1. \( A(adj A^{T}) = A(adj A)^{T} \)
2. If \( A^{2} = A \), then A is identity matrix of order n
3. If \( A^{3} = A \), then A is identity matrix of order n
Which of the statements given above are correct?
A.
1 and 2 only
B.
2 and 3 only
C.
1 and 3 only
D.
1, 2 and 3
ANSWER :
A. 1 and 2 only
13.
How many four-digit natural numbers are there such that all of the digits are even?
A.
625
B.
500
C.
400
D.
256
ANSWER :
B. 500
14.
If \( \omega \neq 1 \) is a cube root of unity, then what are the solutions of \( (z - 100)^{3} + 1000 = 0 \)?
A.
\( 10(1 - \omega), 10(10 - \omega^{2}), 100 \)
B.
\( 10(10 - \omega), 10(10 - \omega^{2}), 90 \)
C.
\( 10(1 - \omega), 10(10 - \omega^{2}), 1000 \)
D.
\( (1 + \omega), (10 + \omega^{2}), -1 \)
ANSWER :
B. \( 10(10 - \omega), 10(10 - \omega^{2}), 90 \)
15.
What is \( (1 + i)^{4} + (1 - i)^{4} \) equal to, where \( i = \sqrt{-1} \)?
A.
4
B.
0
C.
−4
D.
−8
ANSWER :
D. −8
16.
Consider the following statements in respect of a skew-symmetric matrix A of order 3:
1. All diagonal elements are zero.
2. The sum of all the diagonal elements of the matrix is zero.
3. A is orthogonal matrix.
Which of the statements given above are correct?
A.
1 and 2 only
B.
2 and 3 only
C.
1 and 3 only
D.
1, 2 and 3
ANSWER :
A. 1 and 2 only
17.
Four digit numbers are formed by using the digits 1, 2, 3, 5 without repetition of digits. How many of them are divisible by 4?
A.
120
B.
24
C.
12
D.
6
ANSWER :
D. 6
18.
What is the remainder when \( 2^{120} \) is divided by 7?
A.
1
B.
3
C.
5
D.
6
ANSWER :
A. 1
19.
For what value of n is the determinant
\( \begin{vmatrix} C(9,4) & C(9,3) & C(10,n-2) \\ C(11,6) & C(11,5) & C(12,n) \\ C(m,7) & C(m,6) & C(m+1,n+1) \end{vmatrix} = 0 \)
for every m > n?
A.
4
B.
5
C.
6
D.
7
ANSWER :
C. 6
20.
If ABC is a triangle, then what is the value of the determinant
\( \begin{vmatrix} \cos C & \sin B & 0 \\ \tan A & 0 & \sin B \\ 0 & \tan(B + C) & \cos C \end{vmatrix} \)?
A.
−1
B.
0
C.
1
D.
3
ANSWER :
B. 0