NDA & NA Exam (I)- 2017 - Mathematics Defence Question Paper

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NDA & NA Exam (I)- 2017 - Mathematics

NDA & NA Exam (I)- 2017 - Mathematics Defence Questions

21.
The sum of all the two-digit odd numbers is
A.
2475
B.
2530
C.
4905
D.
5049
ANSWER :
A. 2475
22.
The sum of the first n terms of the series \( \frac{1}{2} + \frac{3}{4} + \frac{7}{8} + \frac{15}{16} + \ldots \) is equal to
A.
\( 2^{n} - n - 1 \)
B.
\( 1 - 2^{-n} \)
C.
\( 2^{-n} + n - 1 \)
D.
\( 2^{n} - 1 \)
ANSWER :
C. \( 2^{-n} + n - 1 \)
23.
Consider the following in respect of sets A and B:
1. \( (A - B) \cup B = A \)
2. \( (A - B) \cup A = A \)
3. \( (A - B) \cap B = \phi \)
4. \( A \subseteq B \Rightarrow A \cup B = B \)
Which of the above are correct?
A.
1, 2 and 3
B.
2, 3 and 4
C.
1, 3 and 4
D.
1, 2 and 4
ANSWER :
B. 2, 3 and 4
24.
In the binary equation \( (1p101)_{2} + (10q1)_{2} = (100r00)_{2} \), where p, q and r are binary digits, what are the possible values of p, q and r respectively?
A.
0, 1, 0
B.
1, 1, 0
C.
0, 0, 1
D.
1, 0, 1
ANSWER :
A. 0, 1, 0
25.
If \( S = \{x : x^{2} + 1 = 0\} \), where x is real, then S is
A.
{−1}
B.
{0}
C.
{1}
D.
an empty set
ANSWER :
D. an empty set
26.
The expansion of \( (x - y)^{n} \), \( n \geq 5 \) is done in the descending powers of x. If the sum of the fifth and sixth terms is zero, then \( \frac{x}{y} \) is equal to
A.
\( \frac{n-5}{6} \)
B.
\( \frac{n-4}{5} \)
C.
\( \frac{5}{n-4} \)
D.
\( \frac{6}{n-5} \)
ANSWER :
B. \( \frac{n-4}{5} \)
27.
If \( A = \begin{bmatrix} \alpha & 2 \\ 2 & \alpha \end{bmatrix} \) and \( \det(A^{3}) = 125 \), then \( \alpha \) is equal to
A.
\( \pm 1 \)
B.
\( \pm 2 \)
C.
\( \pm 3 \)
D.
\( \pm 5 \)
ANSWER :
C. \( \pm 3 \)
28.
If B is a non-singular matrix and A is a square matrix, then the value of \( \det(B^{-1}AB) \) is equal to
A.
det (B)
B.
det (A)
C.
\( \det(B^{-1}) \)
D.
\( \det(A^{-1}) \)
ANSWER :
B. det (A)
29.
If \( a \neq b \neq c \), then one value of x which satisfies the equation \( \begin{vmatrix} 0 & x-a & x-b \\ x+a & 0 & x-c \\ x+b & x+c & 0 \end{vmatrix} = 0 \) is given by
A.
a
B.
b
C.
c
D.
0
ANSWER :
D. 0
30.
If \( A = \begin{bmatrix} \cos\alpha & \sin\alpha \\ -\sin\alpha & \cos\alpha \end{bmatrix} \), then what is \( AA^{T} \) equal to (where \( A^{T} \) is the transpose of A)?
A.
Null matrix
B.
Identity matrix
C.
A
D.
−A
ANSWER :
B. Identity matrix