engineering-mathematics

Question 2
 For two n-dimensional real vectors P and Q, the operation s(P, Q) is defined as follows:
A
10
B
11
C
9
D
100
Question 2 Explanation: 

s(P,Q) is the sum of dot products of vectors P and Q in each dimension.  The 0 dot product indicates that the vectors must be orthogonal to each other. 
In a n-dimensional space, we have n axes  orthogonal to each other.  It is given that for every pair the dot product must be 0, then at most n vectors each mentioning each dimension can be considered.  Thus for 10 dimensional space’s set of vectors ℒ , 10 mutually orthogonal vectors can be present. 

Question 3
A bag has r red balls and b black balls. All balls are identical except for their colours. In a trial, a ball is randomly drawn from the bag, its colour is noted and the ball is placed back into the bag along with another ball of the same colour. Note that the number of balls in the bag will increase by one, after the trial. A sequence of four such trials is conducted. Which one of the following choices gives the probability of drawing a red ball in the fourth trial?
A
B
C
D
E
Question 3 Explanation: 
  • There are 8 ways to get ‘red’ in the fourth attempt of drawing 

    i.e., _ _ _ R these three gaps can be filled with B/R in 222=8 ways

    The probability for case (1),


Question 4
 Let S be a set consisting of 10 elements. The number of tuples of the form (A, B) such that A and B are subsets of S, and A ⊆ B is _________.
A
59049
Question 4 Explanation: 
Question 5
. Suppose that P is a 45matrix such that every solution of the equation Px=0 is a scalar multiple of [2  5  4  3  1]T. The rank of P is _________.
A
4
Question 5 Explanation: 
If the rank of a homogeneous system is less than the number of variables in the system, then the system has infinitely many solutions. r
Question 6
In an examination, a student can choose the order in which two questions (QuesA and QuesB) must be attempted.
  • If the first question is answered wrong, the student gets zero marks.
  • If the first question is answered correctly and the second question is not answered correctly, the student gets the marks only for the first question.  
  • If both the questions are answered correctly, the student gets the sum of the marks of the two questions.
The following table shows the probability of correctly answering a question and the marks of the question respectively.
question Probability of answering correctly marks
QuesA QuesB 0.8 0.5 10 20
Assuming that the student always wants to maximize her expected marks in the examination, in which order should she attempt the questions and what is the expected marks for that order (assume that the questions are independent)?
A
First QuesB and then QuesA. Expected marks 22.
B
First QuesA and then QuesB. Expected marks 16.
C
First QuesA and then QuesB. Expected marks 14.
D
First QuesB and then QuesA. Expected marks 14.
Question 6 Explanation: 

There are two ways to get marks.
1. Answering first question correctly, and second one wrongly
2. Answering first question and second question correctly.

There are two ways to answer the question paper. First A or First B.
In total we get 4 ways of answering the paper to get marks. 

Note: Answering each question is independent, thus P(x intersection y) = P(x)*P(y)|
P(Answering A correctly) =0.8, P( Answering A wrongly) = 1-0.8=0.2
P(Answering B correctly) =0.5, P( Answering B wrongly) = 1-0.5=0.5



 

Probability of Getting marks 

Marks 

First A correctly, B wrongly

P(A correctly)*P(B wrongly)
= 0.8*0.5 = 0.4

10+0 = 10

First A correctly B correctly

P(A correctly)*P(B Correctly)
= 0.8*0.5 = 0.4

10+20 = 30

First B correctly, A wrongly

P(B correctly)*P(A wrongly)
= 0.5*0.2 = 0.1

20+0=20

First B correctly then A correctly

P(B correctly)*P(A Correctly)
=0.5*0.8 = 0.4

20+10=30

 

Expectation formula
                                   

                                         E(X)=∑X*P(X)

 

   Expectation for the order:A followed by B = 0.4*10 +0.4*30 = 16
Expectation for the order B followed by A = 0.1*20 + 0.4*30 = 14

 

As the target is to get maximum marks, the order A followed by B is the correct option

Question 7
Choose the correct choice(s) regarding the following propositional logic assertion S:
A
S is a contradiction.
B
The anecdote of S is logically equivalent to the consequent of S.
C
S is a tautology.
D
S is neither a tautology nor a contradiction.
Question 7 Explanation: 
Question 8
A
There exists a bijection from S1to S2.
B
There does not exist a bijection from S1to S2.
C
There exists a surjection from S1to S2.
D
There does not exist an injunction from S1to S2.
Question 8 Explanation: 

The number of functions from a set A to set B is |B|^|A|.

S2: |B|= 3, |A|= n^2-1 +1 = n^2.
we have number of functions 3^(n^2).

S1: there are n*n positions in a matrix of size nxn. Each can be filled with either 0 or 1 or 2 i,e, in 3^(n^2)

 

As there are equal number of elements on both sides, S1->S2 can be one one , onto as well bijection



Question 9
For a given biased coin, the probability that the outcome of a toss is a head is 0.4. This coin is tossed 1,000 times. Let X denote the random variable whose value is the number of times that head appeared in these 1,000 tosses. The standard deviation of X (rounded to 2 decimal places) is _______.
A
15.49
Question 9 Explanation: 
Question 10

The probability that a number selected at random between 100 and 999 (both inclusive) will not contain the digit 7 is:

A
16/25
B
(9/10)3
C
27/75
D
18/25
Question 10 Explanation: 
Question 11

Let R be a symmetric and transitive relation on a set A. Then

A
R is reflexive and hence an equivalence relation
B
R is reflexive and hence a partial order
C
R is reflexive and hence not an equivalence relation
D
None of the above
Question 11 Explanation: 
If a relation is equivalence then it must be
i) Symmetric
ii) Reflexive
iii) Transitive
If a relation is said to be symmetric and transitive then we can't say the relation is reflexive and equivalence.
Question 12

The number of elements in he power set P (S) of the set S = {(φ), 1, (2, 3)} is:

A
2
B
4
C
8
D
None of the above
Question 12 Explanation: 
S = {(φ), 1, (2, 3)}
P(S) = {φ, {{φ}}, {1}, {{2, 3}}, {{φ}, 1}, {1, {2, 3}}, {{φ}, 1, {2, 3}}}
In P(S) it contains 8 elements.
Question 13

In the interval [0, π] the equation x = cos x has

A
No solution
B
Exactly one solution
C
Exactly two solutions
D
An infinite number of solutions
Question 13 Explanation: 

x & cos(x) are intersecting at only one point.
Question 14

If at every point of a certain curve, the slope of the tangent equals −2x/y the curve is

A
a straight line
B
a parabola
C
a circle
D
an ellipse
Question 14 Explanation: 
Note: Out of syllabus.
Question 15

The value of k for which 4x2 - 8xy + ky2 = 0 does not represent a pair of straight lines (both passing through the origin) is:

A
0
B
2
C
9
D
3
Question 15 Explanation: 
Note: Out of syllabus.
Question 16

The rank of the following (n + 1)×(n+1) matrix, where a is a real number is

A
1
B
2
C
n
D
Depends on the value of a
Question 16 Explanation: 
Question 17

The minimum number of edges in a connected cyclic graph on n vertices is:

A
n - 1
B
n
C
n + 1
D
None of the above
Question 17 Explanation: 
In a normal graph number of edges required for n vertices is n-1, and in cyclic graph it is n.
In cyclic graph:
No. of edges = No. of vertices
⇒ n = n
Question 18

If the cube roots of unity are 1, ω and ω2, then the roots of the following equation are (x - 1)3 + 8 = 0

A
-1, 1 + 2ω, 1 + 2ω2
B
1, 1 - 2ω, 1 - 2ω2
C
-1, 1 - 2ω, 1 - 2ω2
D
-1, 1 + 2ω, -1 + 2ω2
Question 18 Explanation: 
Just put values of (C) in place of x. It will satisfy the equation.
Question 19

A language with string manipulation facilities uses the following operations

 head(s): first character of a string
 tail(s): all but the first character of a string
 concat(s1,s2):s1 s2
 for the string acbc what will be the output of
 concat(head(s), head(tail(tail(s)))) 
A
ac
B
bc
C
ab
D
cc
Question 19 Explanation: 
concat (a, head (tail (tail (acbc))))
concat (a, head (tail (cbc)))
concat (a, head (bc))
concat (a, b)
ab
Question 20

A unit vector perpendicular to both the vectors a = 2i - 2j + k and b = 1 + j - 2k is:

A
1/√3 (1+j+k)
B
1/3 (1+j-k)
C
1/3 (1-j-k)
D
1/√3 (1+j-k)
E
None of the above.
Question 20 Explanation: 
Dot product of two perpendicular vectors must be zero.
Question 21

A bag contains 10 white balls and 15 black balls. Two balls are drawn in succession. The probability that one of them is black and the other is white is:

A
2/3
B
4/5
C
1/2
D
2/1
Question 21 Explanation: 
Probability of first ball white and second one black is,

Probability of first ball black and second one white is,
Question 22

The iteration formula to find the square root of a positive real number b using the Newton Raphson method is

A
B
C
D
None of the above
Question 22 Explanation: 
Note: Out of syllabus.
Question 23

Let A be the set of all non-singular matrices over real number and let* be the matrix multiplication operation. Then

A
A is closed under* but < A, *> is not a semigroup
B
is a semigroup but not a monoid
C
is a monoid but not a group
D
is a group but not an abelian group
Question 23 Explanation: 
As the matrices are non-singular so their determinant ±0. Hence, the inverse matrix always exist. But for a group to be Abelian it should follow commutative property. As matrix multiplication is not commutative, is a group but not an abelian group.
Question 24

The solution of differential equation y'' + 3y' + 2y = 0 is of the form

A
C1ex + C2e2x
B
C1e-x + C2e3x
C
C1e-x + C2e-2x
D
C1e-2x + C22-x
Question 24 Explanation: 
Note: Out of syllabus.
Question 25

If the proposition ¬p ⇒ ν is true, then the truth value of the proposition ¬p ∨ (p ⇒ q), where ¬ is negation, ‘∨’ is inclusive or and ⇒ is implication, is

A
true
B
multiple valued
C
false
D
cannot be determined
Question 25 Explanation: 
From the axiom ¬p → q, we can conclude that p ∨ q.
So, either p or q must be True.
Now,
¬p ∨ (p → q)
= ¬p ∨ (¬p ∨ q)
= ¬p ∨ q
Since nothing c an be said about the truth values of p, it implies that ¬p ∨ q can also be True or False. Hence, the value cannot be determined.
Question 26

(a) Determine the number of divisors of 600.
(b) Compute without using power series expansion

A
Theory Explanation.
Question 27

Obtain the principal (canonical) conjunctive normal form of the propositional formula

  (p ∧ q) V (¬q ∧ r) 

Where ‘∧’ is logical and, ‘v’ is inclusive or and ¬ is negation.

A
Theory Explanation.
Question 28

Let G1 and G2 be subgroups of a group G.
(a) Show that G1 ∩ G2 is also a group of G.
(b) Is G1 ∪ G2 always a subgroup of G?

A
Theory Explanation.
Question 29

Prove using mathematical induction for n≥5, 2n > n2

A
Theory Explanation.
Question 30

Prove that in finite graph, the number of vertices of odd degree is always even.

A
Theory Explanation.
Question 31

(a) Find the minimum value of 3 - 4x + 2x2.
(b) Determine the number of positive integers (≤ 720) which are not divisible by any of numbers 2, 3, and 5.

A
Theory Explanation.
Question 32

Let G be a group of 35 elements. Then the largest possible size of a subgroup of G other than G itself is ______.

A
7
Question 32 Explanation: 
Lagrange’s Theorem:
If ‘H” is a subgroup of finite group (G,*) then O(H) is the divisor of O(G).
Given that the order of group is 35. Its divisors are 1,5,7,35.
It is asked that the size of largest possible subgroup other than G itself will be 7.
Question 33

Let R be the set of all binary relations on the set {1,2,3}. Suppose a relation is chosen from R at random. The probability that the chosen relation is reflexive (round off to 3 decimal places) is _____.

A
0.125
Question 33 Explanation: 
For a set with n elements,
The number of reflexive relations is 2^(n^2-n).
The total number of relations on a set with n elements is 2^ (n^2).
The probability of choosing the reflexive relation out of set of relations is
= 2^(n^2-n) /2^ (n^2)
= 2^( n^2-n- n^2)
= 2^(-n)
Given n=3, the probability will be 2-n = ⅛ = 0.125
Question 34

Consider the functions

    I. e-x
    II. x2-sin x
    III. √(x3+1)

Which of the above functions is/are increasing everywhere in [0,1]?

A
II and III only
B
III only
C
II only
D
I and III only
Question 34 Explanation: 
A function f(x) is said to be increasing if f'(x)>0 at each point in an interval.
I. e-x
II. f'(x) = -e-x
f'(x)<0 on the interval [0,1] so this is not an increasing function.
II. x2-sinx
f'(x) = 2x - cosx
at x=0, f'(0) = 2(0) - 1 = -1 < 0
f(x) = x2 - sinx is decreasing over some interval, increasing over some interval as cosx is periodic.
As the question is asked about increasing everywhere II is false.
III. √(x3+1) = (x3+1)1/2
f'(x) = 1/2(3x2/√(x3+1))>0
f(x) is increasing over [0,1].
Question 35

For n>2, let a ∈ {0,1}n be a non-zero vector. Suppose that x is chosen uniformly at random from {0,1}n. Then, the probability that  is an odd number is _____.

A
0.5
Question 35 Explanation: 
‘a’ is a non-zero vector such that a∈{0,1}n
‘x’ is a vector chosen randomly from {0,1}n
‘a’ can have 2(n-1) possibilities, x can have 2n possibilities.
∑aixi have (2n-1)(2n) possibilities, which is an even number of outcomes.
The probability of https://solutionsadda.in/wp-content/uploads/2020/02/41.jpg is odd is ½.
For example:
Take n=3
a = {001, 010, 100, 011, 101, 111}
x = {000, 001, 010, 011, 100, 101, 110, 111}
Computed as [001]×[000] = 0+0+0 = 0 Output = even
[001]×[001] = 0+0+1 = 0 Output = odd
Similarly, there could be 28 even, 28 odd outputs for the a(size=7), x(size=8) of total 56 outputs.
Question 36

Graph G is obtained by adding vertex s to K3,4 and making s adjacent to every vertex of K3,4. The minimum number of colours required to edge-colour G is _____.

A
7
Question 36 Explanation: 
In k3x4 there are two sets with sizes 3,4. (it is a complete bipartite graph).
The vertex in the set of size 3 has 4 edges connected to 4 vertices on other set. So, edge color of G is max(3,4) i.e. 4.
When a vertex is added to the graph with 7 vertices ( K3x4 has 7 vertices), there would be 7 edges associated to that new vertex. As per the edge coloring “no two adjacent edges have same color).
As the new vertex with 7 edges need to be colored with 7 colors, the edge color of graph G is 7.
Question 37

Which one of the following predicate formulae is NOT logically valid?
Note that W is a predicate formula without any free occurrence of x.

A
∃x(p(x) → W) ≡ ∀x p(x) → W
B
∀x(p(x) → W) ≡ ∀x p(x) → W
C
∃x(p(x) ∧ W) ≡ ∃x p(x) ∧ W
D
∀x(p(x) ∨ W) ≡ ∀x p(x) ∨ W
Question 37 Explanation: 
Basic Rules:
~p→q ≡ ~p∨q
Demorgan laws:
~(∀x(a(x)) ≡ ∃x~a(x)
~(∃x(a(x)) ≡ ∀x~a(x)
(A) ∃x(p(x)→w) ≡ ∀x p(x)→w
LHS: ∃x(p(x)→w) ≡ ∃x(~p(x)∨w)
≡ ∃x(~p(x))∨w
Demorgan’s law:
~(∀x(a(x)) = ∃x ~ a(x)
≡ ~(∀x P(x)) ∨ w
≡ (∀x) P(x) → w ≡ RHS
It’s valid.
(B) ∀x(P(x) → w) ≡ ∀x(~P(x) ∨ w)
≡ ∀x(~P(x)) ∨ w
≡ ~(∃x P(x)) ∨ w
≡ ∃x P(x) → w
This is not equal to RHS.
(C) ∃x(P(x) ∧ w) ≡ ∃x P(x) ∧ w
‘w’ is not a term which contains x.
So the quantifier does not have any impact on ‘w’.
Thus it can be written as
∃x(P(x)) ∧ w) ≡ ∃x P(x) ∧ w
(D) ∀(x)(P(x) ∨ w) ≡ ∀x P(x) ∨ w
‘w’ is not a term which contains ‘x’.
So the quantifier does not have an impact on ‘w’.
Thus ∀(x)(P(x) ∨ w) ≡ ∀x P(x) ∨ w
Question 38

The number of permutations of the characters in LILAC so that no character appears in its original position, if the two L’s are indistinguishable, is _______.

A
12
Question 38 Explanation: 
There are 5 places.
― ― ― ― ―
Given: L I L A C
The derangement formula ⎣n!/e⎦ cannot be directly performed as there are repeated characters.
Let’s proceed in regular manner:
The L, L can be placed in other ‘3’ places as

(1) Can be arranged such that A, I, C be placed in three positions excluding ‘C’ being placed at its own position, which we get only 2×2×1 = 4 ways.
Similarly (2) can be filled as A, I, C being placed such that 4th position is not filled by A, so we have 2×2×1 = 4 ways. Similarly with (3).
Totally, we get 4+4+4 = 12 ways.
Question 39

Let A and B be two n×n matrices over real numbers. Let rank(M) and det(M) denote the rank and determinant of a matrix M, respectively. Consider the following statements,

    I. rank(AB) = rank(A) rank(B)
    II. det(AB) = det(A) det(B)
    III. rank(A + B) ≤ rank(A) + rank(B)
    IV. det(A + B) ≤ det(A) + det(B)

Which of the above statements are TRUE?

A
I and II only
B
I and IV only
C
III and IV only
D
II and III only
Question 39 Explanation: 
Rank(AB) ≥ Rank(A) + Rank(B) − n. So option I is wrong.
Rank is the number of independent rows(vectors) of a matrix. On product of two matrices, the combined rank is more than the sum of individual matrices (subtracted with the order n)
det(AB) = det(A)∙det(B) as the magnitude remains same for the matrices after multiplication.
Note: We can just take a 2x2 matrix and check the options.
Question 40

Let A and B be sets and let Ac and Bc denote the complements of the sets A and B. The set (A – B) ∪ (B - A) ∪ (A∩B) is equal to

A
A ∪ B
B
Ac ∪ Bc
C
A ∩ B
D
Ac ∩ Bc
Question 40 Explanation: 
(A – B) ∪ (B - A) ∪ (A∩B)

(A - B) = 1
(B - A) = 2
(A∩B) = 3
A∪B = (1∪2∪3)
(A – B) ∪ (B - A) ∪ (A∩B) = 1∪2∪3 = (A∪B)
Question 41

Let X = {2,3,6,12,24}, Let ≤ be the partial order defined by X ≤ Y if x divides y. Number of edge as in the Hasse diagram of (X,≤) is

A
3
B
4
C
9
D
None of the above
Question 41 Explanation: 

No. of edges = 4
Question 42

Suppose X and Y are sets and X Y and are their respective cardinalities. It is given that there are exactly 97 functions from X to Y. from this one can conclude that

A
|X| = 1, |Y| = 97
B
|X| = 97, |Y| = 1
C
|X| = 97, |Y| = 97
D
None of the above
Question 42 Explanation: 
From the given information we can write,
|Y||X| = 97
→ Option A only satisfies.
Question 43

Which of the following statements is false?

A
The set of rational numbers is an abelian group under addition.
B
The set of integers in an abelian group under addition.
C
The set of rational numbers form an abelian group under multiplication.
D
The set of real numbers excluding zero in an abelian group under multiplication.
Question 43 Explanation: 
Rational number consists of number '0'. If 0 is present in a set inverse is not possible under multiplication.
Question 44

Two dice are thrown simultaneously. The probability that at least one of them will have 6 facing up is

A
1/36
B
1/3
C
25/36
D
11/36
Question 44 Explanation: 
1 - no. 6 on both dice
1 - (5/6 × 5/6) = 1 - (25/36) = 11/36
Question 45

The formula used to compute an approximation for the second derivative of a function f at a point X0 is

A
f(x0+h) + f(x0-h)/2
B
f(x0+h) - f(x0-h)/2h
C
f(x0+h) + 2f(x0) + f(x0-h)/h2
D
f(x0+h) - 2f(x0) + f(x0-h)/h2
Question 45 Explanation: 
The formula which is used to compute the second derivation of a function f at point X is
f(x0+h) - 2f(x0) + f(x0-h)/h2
Question 46

Let Ax = b be a system of linear equations where A is an m × n matrix and b is a m × 1 column vector and X is a n × 1 column vector of unknowns. Which of the following is false?

A
The system has a solution if and only if, both A and the augmented matrix [A b] have the same rank.
B
If m < n and b is the zero vector, then the system has infinitely many solutions.
C
If m = n and b is non-zero vector, then the system has a unique solution.
D
The system will have only a trivial solution when m = n, b is the zero vector and rank (A) = n.
Question 46 Explanation: 
→ It belongs to linear non-homogeneous equations. So by having m=n, we can't say that it will have unique solution.
→ Solution can be depends on rank of matrix A and matrix [A B].
→ If rank[A] = rank[A B] then it can have solution otherwise no solution.
Question 47

Let R denotes the set of real numbers. Let f: R×R → R×R be a bijective function defined by f(x,y) = (x+y,x-y), The inverse function of f is given by

A
B
C
D
Question 47 Explanation: 
Question 48

Let R be a non-empty relation on a collection of sets defined by A R B if and only if A ∩ B = ф. Then, (pick the true statement)

A
R is reflexive and transitive
B
R is symmetric and not transitive
C
R is an equivalence relation
D
R is not reflexive and not symmetric
Question 48 Explanation: 
Let A = {1, 2, 3} and B = {4, 5} and C = {1, 6, 7}
Now,
A ∩ B = ф
& B ∩ C = ф
But A ∩ B ≠ ф
So, R is not transitive.
A ∩ B = A, so R is not reflexive.
If A ∩ B = ф
then definitely B ∩ A = ф.
Hence, R is symmetric.
So, option (B) is true.
Question 49

Which of the following is false? Read ∧ as AND, ∨ as OR, ~ as NOT, → as one way implication and ↔ as two way implication.

A
((x → y) ∧ x) → y
B
((x → y) ∧ (x ∧ y)) → x
C
(x → (x ∨ ψ))
D
((x ∨ y) ↔ (x → y)
Question 49 Explanation: 
When x = F and y = F
then option (D) will be False.
Question 50

Which one of the following is false?

A
The set of all bijective functions on a finite set forms a group under function composition.
B
The set {1, 2, ……., p–1} forms a group under multiplication mod p where p is a prime number.
C
The set of all strings over a finite alphabet forms a group under concatenation.
D
A subset s ≠ ф of G is a subgroup of the group if and only if for any pair of elements a, b ∈ s, a* b-1 ∈ s.
Question 50 Explanation: 
Option (C) is False because string concatenation operation is monoid (doesn't have inverse to become a group).
There are 50 questions to complete.

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