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

NDA Previous Year Question Papers Question Papers
NDA & NA Exam (II)- 2025 - Mathematics

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

11.
In a class of 45 students, 34 like to play cricket and 26 like to play football. Further, each student likes to play at least one of the two games. How many students like to play exactly one game?
A.
45
B.
30
C.
25
D.
15
ANSWER :
B. 30
12.
The system of equations \( 2x - 3y - 5 = 0 \), \( 15y - 10x + 50 = 0 \)
A.
has a unique solution
B.
has infinitely many solutions
C.
is inconsistent
D.
is consistent and has exactly two solutions
ANSWER :
C. is inconsistent
13.
If
\( \left(\frac{1 - i}{1 + i}\right)^{m}\left(\frac{1 + i}{1 - i}\right)^{n} = 1 \)
where \( i = \sqrt{-1} \), then what is the smallest positive value of \( (m - n) \)?
A.
1
B.
2
C.
4
D.
8
ANSWER :
C. 4
14.
In obtaining the solution of the system of equations \( x + y + z = 7 \), \( x + 2y + 3z = 16 \) and \( x + 3y + 4z = 22 \) by Cramer's rule, the value of \( y \) is obtained by dividing \( D_{2} \) by \( D \), where
\( D = \begin{vmatrix} 1 & 1 & 1 \\ 1 & 2 & 3 \\ 1 & 3 & 4 \end{vmatrix} \)
What is the value of the determinant \( D_{2} \)?
A.
-13
B.
-3
C.
3
D.
13
ANSWER :
B. -3
15.
Consider the following in respect of non-singular matrices \( A \) and \( B \):
I. \( (AB)^{-1} = A^{-1}B^{-1} \)
II. \( (BA)(AB)^{-1} = I \), where \( I \) is the identity matrix
III. \( (AB)^{T} = A^{T}B^{T} \)
How many of the above are correct?
A.
None
B.
One
C.
Two
D.
All three
ANSWER :
A. None
16.
The value of the determinant
\( \begin{vmatrix} a & b & c \\ l & m & n \\ p & q & r \end{vmatrix} \)
is equal to
A.
\( \begin{vmatrix} a & b & c \\ p & q & r \\ l & m & n \end{vmatrix} \)
B.
\( \begin{vmatrix} l & m & n \\ a & b & c \\ p & q & r \end{vmatrix} \)
C.
\( \begin{vmatrix} p & q & r \\ a & b & c \\ l & m & n \end{vmatrix} \)
D.
\( \begin{vmatrix} a & p & l \\ b & q & m \\ c & r & n \end{vmatrix} \)
ANSWER :
C. \( \begin{vmatrix} p & q & r \\ a & b & c \\ l & m & n \end{vmatrix} \)
17.
Let \( 1, \omega, \omega^{2} \) be three cube roots of unity. If \( x = a + b \), \( y = a\omega + b\omega^{2} \), \( z = a\omega^{2} + b\omega \), then what is \( x^{2} + y^{2} + z^{2} \) equal to?
A.
\( 6ab \)
B.
\( 3ab \)
C.
\( a^{2} + b^{2} \)
D.
1
ANSWER :
A. \( 6ab \)
18.
How many 4-digit numbers that are divisible by 4 can be formed using the digits 1, 2, 3 and 4 (repetition of digits is not allowed)?
A.
3
B.
6
C.
9
D.
12
ANSWER :
B. 6
19.
If \( a, b, c \) are the sides of a triangle ABC and \( p \) is the perimeter of the triangle, then what is
\( \begin{vmatrix} p+c & a & b \\ c & p+a & b \\ c & a & p+b \end{vmatrix} \)
equal to?
A.
\( p^{3} \)
B.
\( 2p^{3} \)
C.
\( 3p^{3} \)
D.
\( 4p^{3} \)
ANSWER :
B. \( 2p^{3} \)
20.
Which one of the following is the greatest coefficient in the expansion of \( (1 + x)^{100} \)?
A.
The coefficient of \( x^{100} \)
B.
The coefficient of \( x^{99} \)
C.
The coefficient of \( x^{51} \)
D.
The coefficient of \( x^{50} \)
ANSWER :
D. The coefficient of \( x^{50} \)