NDA & NA Exam (I)- 2025 - Mathematics Defence Question Paper

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NDA & NA Exam (I)- 2025 - Mathematics

NDA & NA Exam (I)- 2025 - Mathematics Defence Questions

11.
If \( A + B + C = \pi \), then what is the value of the following?
\( \begin{vmatrix} 1 & \cos C & \cos B \\ \cos C & 1 & \cos A \\ \cos B & \cos A & 1 \end{vmatrix} \)
A.
-1
B.
0
C.
1
D.
2
ANSWER :
B. 0
12.
If \( \omega \) is a non-real cube root of unity, then what is a root of the following equation?
\( \begin{vmatrix} x+1 & \omega & \omega^{2} \\ \omega & x+\omega^{2} & 1 \\ \omega^{2} & 1 & x+\omega \end{vmatrix} = 0 \)
A.
\( x = 0 \)
B.
\( x = 1 \)
C.
\( x = \omega \)
D.
\( x = \omega^{2} \)
ANSWER :
A. \( x = 0 \)
13.
What is \( \left(\frac{\sqrt{3} + i}{\sqrt{3} - i}\right)^{3} \) equal to?
A.
-1
B.
0
C.
1
D.
3
ANSWER :
A. -1
14.
If \( x^{2} - x + 1 = 0 \), then what is
\( \left(x - \frac{1}{x}\right)^{2} + \left(x - \frac{1}{x}\right)^{4} + \left(x - \frac{1}{x}\right)^{8} \)
equal to?
A.
81
B.
85
C.
87
D.
90
ANSWER :
C. 87
15.
How many 7-letter words (with or without meaning) can be constructed using all the letters of the word CAPITAL so that all consonants come together in each word?
A.
360
B.
300
C.
288
D.
240
ANSWER :
C. 288
16.
If \( z \neq 0 \) is a complex number, then what is \( amp(z) + amp(\bar{z}) \) equal to?
A.
0
B.
\( \frac{\pi}{2} \)
C.
\( \pi \)
D.
\( 2\pi \)
ANSWER :
A. 0
17.
How many sides are there in a polygon which has 20 diagonals?
A.
6
B.
7
C.
8
D.
10
ANSWER :
C. 8
18.
In how many ways can the letters of the word DELHI be arranged keeping the positions of vowels and consonants unchanged?
A.
6
B.
9
C.
12
D.
24
ANSWER :
C. 12
19.
What is the number of positive integer solutions of \( x + y + z = 5 \)?
A.
3
B.
5
C.
6
D.
9
ANSWER :
C. 6
20.
What is the number of rational terms in the expansion of \( \left(3^{\frac{1}{2}} + 5^{\frac{1}{4}}\right)^{12} \)?
A.
2
B.
3
C.
4
D.
6
ANSWER :
C. 4