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

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NDA & NA Exam (I)- 2023 - Mathematics

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

1.
If \( \omega \) is a non-real cube root of 1, then what is the value of \( \left|\frac{1 - \omega}{\omega + \omega^{2}}\right| \)?
A.
\( \sqrt{3} \)
B.
\( \sqrt{2} \)
C.
1
D.
\( \frac{1}{\sqrt{3}} \)
ANSWER :
A. \( \sqrt{3} \)
2.
What is the number of 6-digit numbers that can be formed only by using 0, 1, 2, 3, 4 and 5 (each once); and divisible by 6?
A.
96
B.
120
C.
192
D.
312
ANSWER :
D. 312
3.
What is the binary number equivalent to decimal number 1011?
A.
1011
B.
111011
C.
11111001
D.
1111110011
ANSWER :
D. 1111110011
4.
Let \( A \) be a matrix of order \( 3 \times 3 \) and \( |A| = 4 \). If \( |2 adj(3A)| = 2^{\alpha} 3^{\beta} \), then what is the value of \( (\alpha + \beta) \)?
A.
12
B.
13
C.
17
D.
24
ANSWER :
B. 13
5.
If \( \alpha \) and \( \beta \) are the distinct roots of equation \( x^{2} - x + 1 = 0 \), then what is the value of \( \left|\frac{\alpha^{100} + \beta^{100}}{\alpha^{100} - \beta^{100}}\right| \)?
A.
\( \sqrt{3} \)
B.
\( \sqrt{2} \)
C.
1
D.
\( \frac{1}{\sqrt{3}} \)
ANSWER :
D. \( \frac{1}{\sqrt{3}} \)
6.
Let \( A \) and \( B \) be symmetric matrices of same order, then which one of the following is correct regarding \( (AB - BA) \)?
1. Its diagonal entries are equal but nonzero
2. The sum of its non-diagonal entries is zero
Select the correct answer using the code given below:
A.
1 only
B.
2 only
C.
Both 1 and 2
D.
Neither 1 nor 2
ANSWER :
B. 2 only
7.
Consider the following statements in respect of square matrices \( A, B, C \) each of same order \( n \):
1. \( AB = AC \Rightarrow B = C \) if \( A \) is non-singular
2. If \( BX = CX \) for every column matrix \( X \) having \( n \) rows then \( B = C \)
Which of the statements given above is/are correct?
A.
1 only
B.
2 only
C.
Both 1 and 2
D.
Neither 1 nor 2
ANSWER :
C. Both 1 and 2
8.
The system of linear equations \( x + 2y + z = 4 \), \( 2x + 4y + 2z = 8 \) and \( 3x + 6y + 3z = 10 \) has
A.
a unique solution
B.
infinite many solutions
C.
no solution
D.
exactly three solutions
ANSWER :
C. no solution
9.
Let \( AX = B \) be a system of 3 linear equations with 3-unknowns. Let \( X_{1} \) and \( X_{2} \) be its two distinct solutions. If the combination \( aX_{1} + bX_{2} \) is a solution of \( AX = B \); where \( a, b \) are real numbers, then which one of the following is correct?
A.
\( a = b \)
B.
\( a + b = 1 \)
C.
\( a + b = 0 \)
D.
\( a - b = 1 \)
ANSWER :
B. \( a + b = 1 \)
10.
What is the sum of the roots of the equation
\( \begin{vmatrix} 0 & x - a & x - b \\ 0 & 0 & x - c \\ x + b & x + c & 1 \end{vmatrix} = 0 \)?
A.
\( a + b + c \)
B.
\( a - b + c \)
C.
\( a + b - c \)
D.
\( a - b - c \)
ANSWER :
B. \( a - b + c \)