NDA & NA Exam (II)- 2022 - Mathematics Defence Question Paper

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NDA & NA Exam (II)- 2022 - Mathematics

NDA & NA Exam (II)- 2022 - Mathematics Defence Questions

11.
Let \( p, q \) \( (p > q) \) be the roots of the quadratic equation \( x^{2} + bx + c = 0 \) where \( c > 0 \). If \( p^{2} + q^{2} - 11pq = 0 \), then what is \( p - q \) equal to?
A.
\( 3\sqrt{c} \)
B.
\( 3c \)
C.
\( 9\sqrt{c} \)
D.
\( 9c \)
ANSWER :
A. \( 3\sqrt{c} \)
12.
What is the diameter of a circle inscribed in a regular polygon of 12 sides, each of length 1 cm?
A.
\( 1 + \sqrt{2} \) cm
B.
\( 2 + \sqrt{2} \) cm
C.
\( 2 + \sqrt{3} \) cm
D.
\( 3 + \sqrt{3} \) cm
ANSWER :
C. \( 2 + \sqrt{3} \) cm
13.
Let \( A = \{7, 8, 9, 10, 11, 12, 13, 14, 15, 16\} \) and let \( f: A \rightarrow \mathbb{N} \) be defined by \( f(x) = \) the highest prime factor of \( x \). How many elements are there in the range of \( f \)?
A.
4
B.
5
C.
6
D.
7
ANSWER :
C. 6
14.
Let \( R \) be a relation from \( \mathbb{N} \) to \( \mathbb{N} \) defined by \( R = \{(x, y): x, y \in \mathbb{N} \) and \( x = y^{2}\} \). Which of the following are not correct?
1. \( (x, x) \in R \) for all \( x \in \mathbb{N} \)
2. \( (x, y) \in R \Rightarrow (y, x) \in R \)
3. \( (x, y) \in R \) and \( (y, z) \in R \Rightarrow (x, z) \in R \)
Select the correct answer using the code given below:
A.
1 and 2 only
B.
2 and 3 only
C.
1 and 3 only
D.
1, 2 and 3
ANSWER :
D. 1, 2 and 3
15.
Consider the following:
1. \( A \cap B = A \cap C \Rightarrow B = C \)
2. \( A \cup B = A \cup C \Rightarrow B = C \)
Which of the above is/are correct?
A.
1 only
B.
2 only
C.
Both 1 and 2
D.
Neither 1 nor 2
ANSWER :
D. Neither 1 nor 2
16.
Directions (Qn. 16-18): Consider the following for the next three (03) items that follow:
Let \( z = \frac{1 + i \sin \theta}{1 - i \sin \theta} \), where \( i = \sqrt{-1} \).

What is the modulus of \( z \)?
A.
1
B.
\( \sqrt{2} \)
C.
\( 1 + \sin^{2} \theta \)
D.
\( \frac{1 + \sin^{2} \theta}{1 - \sin^{2} \theta} \)
ANSWER :
A. 1
17.
What is angle \( \theta \) such that \( z \) is purely real, where \( n \) is an integer?
A.
\( \frac{n\pi}{2} \)
B.
\( \frac{(2n+1)\pi}{2} \)
C.
\( n\pi \)
D.
\( 2n\pi \) only
ANSWER :
C. \( n\pi \)
18.
What is angle \( \theta \) such that \( z \) is purely imaginary, where \( n \) is an integer?
A.
\( \frac{n\pi}{2} \)
B.
\( \frac{(2n+1)\pi}{2} \)
C.
\( n\pi \)
D.
\( 2n\pi \)
ANSWER :
B. \( \frac{(2n+1)\pi}{2} \)
19.
Directions (Qn. 19-21): Consider the following for the next three (03) items that follow:
Let \( P \) be the sum of first \( n \) positive terms of an increasing arithmetic progression A. Let \( Q \) be the sum of first \( n \) positive terms of another increasing arithmetic progression B. Let \( P : Q = (5n + 4) : (9n + 6) \).

What is the ratio of the first term of A to that of B?
A.
1/3
B.
2/5
C.
3/4
D.
3/5
ANSWER :
D. 3/5
20.
What is the ratio of their 10th terms?
A.
11/29
B.
22/49
C.
33/59
D.
44/69
ANSWER :
C. 33/59