NDA & NA Exam (I)- 2018 - Mathematics Defence Question Paper

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NDA & NA Exam (I)- 2018 - Mathematics

NDA & NA Exam (I)- 2018 - Mathematics Defence Questions

1.
If \( n \in N \), then \( 121^{n} - 25^{n} + 1900^{n} - (-4)^{n} \) is divisible by which one of the following?
A.
1904
B.
2000
C.
2002
D.
2006
ANSWER :
B. 2000
2.
If n = (2017)!, then what is \( \frac{1}{\log_{2} n} + \frac{1}{\log_{3} n} + \frac{1}{\log_{4} n} + \ldots + \frac{1}{\log_{2017} n} \) equal to?
A.
0
B.
1
C.
\( \frac{n}{2} \)
D.
n
ANSWER :
B. 1
3.
In the expansion of \( (1 + x)^{43} \), if the coefficients of \( (2r + 1)^{th} \) and \( (r + 2)^{th} \) terms are equal, then what is the value of r (r ≠ 1)?
A.
5
B.
14
C.
21
D.
22
ANSWER :
B. 14
4.
What is the principal argument of \( (-1 - i) \), where \( i = \sqrt{-1} \)?
A.
\( \frac{\pi}{4} \)
B.
\( -\frac{\pi}{4} \)
C.
\( -\frac{3\pi}{4} \)
D.
\( \frac{3\pi}{4} \)
ANSWER :
C. \( -\frac{3\pi}{4} \)
5.
Let \( \alpha \) and \( \beta \) be real numbers and z be a complex number. If \( z^{2} + \alpha z + \beta = 0 \) has two distinct non-real roots with \( Re(z) = 1 \), then it is necessary that
A.
\( \beta \in (-1, 0) \)
B.
\( |\beta| = 1 \)
C.
\( \beta \in (1, \infty) \)
D.
\( \beta \in (0, 1) \)
ANSWER :
C. \( \beta \in (1, \infty) \)
6.
Let A and B be subsets of X and \( C = (A \cap B') \cup (A' \cap B) \), where A′ and B′ are complements of A and B respectively in X. What is C equal to?
A.
\( (A \cup B') - (A \cap B') \)
B.
\( (A' \cup B) - (A' \cap B) \)
C.
\( (A \cup B) - (A \cap B) \)
D.
\( A \cap B \)
ANSWER :
C. \( (A \cup B) - (A \cap B) \)
7.
How many numbers between 100 and 1000 can be formed with the digits 5, 6, 7, 8, 9 if the repetition of digits is not allowed?
A.
\( 3^{5} \)
B.
\( 5^{3} \)
C.
120
D.
60
ANSWER :
D. 60
8.
The number of non-zero integral solutions of the equation \( |1 - 2i|^{x} = 5^{x} \) is
A.
zero (no solution)
B.
one
C.
two
D.
three
ANSWER :
A. zero (no solution)
9.
If the ratio of AM to GM of two positive numbers a and b is 5 : 3, then a : b is equal to
A.
3 : 5
B.
2 : 9
C.
9 : 1
D.
5 : 3
ANSWER :
C. 9 : 1
10.
If the coefficients of \( a^{m} \) and \( a^{n} \) in the expansion of \( (1 + a)^{m+n} \) are \( \alpha \) and \( \beta \), then which one of the following is correct?
A.
\( \alpha = 2\beta \)
B.
\( \alpha = \beta \)
C.
\( 2\alpha = \beta \)
D.
\( \alpha = (m + n)\beta \)
ANSWER :
B. \( \alpha = \beta \)