Engineering-Mathematics

Question 1

where tr() represents the trace of a matrix. Which one of the following holds?
A
Statement 1 is correct and Statement 2 is wrong.
B
Statement 1 is wrong and Statement 2 is correct.
C
Both Statement 1 and Statement 2 are correct.
D
Both Statement 1 and Statement 2 are wrong.
Question 1 Explanation: 
the matrices AB and BA have the same characteristic polynomial, so in particular the same trace, and the same determinant.
(In exam point of view, you can just consider small example and conclude).
So trace of AB = trace of BA
As well
Trace of CD = trace of DC
Question 2
Which of the following statements is/are TRUE for a group G ?
A
B
C
If the order of G is 2 , then G is commutative.
D
If G is commutative, then a subgroup of G need not be commutative.
Question 2 Explanation: 
(A) : True. Circular wait is a necessary condition for the formation of a deadlock.
(B) : False. In a multiple instance graph, a cycle always does not indicate deadlock.
(C) : False. Unsafe state may or may not lead to deadlock.
(D) : True. Since every edge is allocated, that means there are no requests. Hence, cycle is not possible.
Question 3
Consider a simple undirected graph of 10 vertices. If the graph is disconnected, then the maximum number of edges it can have is ____________.
A
36
Question 3 Explanation: 
We obtain maximum number of edges in a disconnected graph, with one isolated vertex and remaining completely connected.
Given 10 vertices,
Then we can have a complete graph with 9 vertices and one isolated verted.
Number of edges in complete graph with 9 edges is n(n-1)/2 = 9*8/2 = 36
Question 4
The number of arrangements of six identical balls in three identical bins is______.
A
7
Question 4 Explanation: 
Given distribution of n identical items into r identical boxes.
As no other condition is given,
We need to consider that distinct distribution will be based on the count of balls.
6 identical balls into 3 identical bins.
That can be done in the combination of
[6,0,0], [5,1,0], [ 4,2,0], [3,3,0], [4,1,1],[3,2,1],[2,2,2]
I.e. in 7 ways
Question 5
The value of the following limit is _____________.
A
1/2
Question 5 Explanation: 

When 0 is substituted, we get 0/0
Apply L- Hospital rule


-1/2
Question 6
Which one of the following is the decimal form of generating function of the sequences {an} n >=0 defined below
A
B
C
D
Question 6 Explanation: 

Question 7
Consider a simple undirected unweighted graph with at least three vertices. If A is the adjacency matrix of the graph, then the number of 3-cycles in the graph is given by the trace of
A
A ^3
B
A^ 3 divided by 2
C
A ^3 divided by 3
D
A ^3 divided by 6
Question 8
Consider solving the following system of simultaneous equations using LU decomposition.
A
B
C
D
Question 8 Explanation: 
The LU decomposition of the given matrix is

Given,

(Assume x1,x2,x3 as a,b,c)






Question 9
The following simple undirected graph is referred to as the Peterson graph.

Which of the following statements is/are TRUE?
A
The chromatic number of the graph is 3.
B
The graph has a Hamiltonian path
C
The following graph is isomorphic to the Peterson graph.
D
The size of the largest independent set of the given graph is 3. (A subset of vertices of a graph form an independent set if no two vertices of the subset are adjacent.)
Question 9 Explanation: 
Chromatic number is 3.

Peterson graph ihas hamiltonian path but not hamiltonian cycle
Given graph in option C is isomorphic as the given has same number of vertice, edges, degree sequence and cycles.
LArgest independent set can be more than 3
Question 10
Which of the properties hold for the adjacency matrix A of a simple undirected unweighted graph having n vertices?
A
The diagonal entries of A 2 are the degrees of the vertices of the graph.
B
If the graph is connected, then none of the entries of A^ n + 1 + I n can be zero.
C
If the sum of all the elements of A is at most 2( n- 1), then the graph must be acyclic.
D
If there is at least a 1 in each of A ’s rows and columns, then the graph must be Connected.
Question 10 Explanation: 
IF A is adjacency matrix, then in the matrix A*A = A^2 we have
The entries aii show the number of 2-length paths between the nodes i and j. Why this happens is easy to see: if there is an edge ij and an edge jk, then there will be a path ik through j. The entries ii are the degrees of the nodes i.
Similarly in A^3 we have the entries aii that show the number of 3-length paths between the nodes i and j.
In A^n-1 + I n, we will have at least n-1 length paths, so there is no possibility of zero entires
Question 11
Which of the following is/are the eigenvector(s) for the matrix given below?
A
B
C
D
Question 11 Explanation: 

Question 12

Let A and B be real symmetric matrices of size n × n. Then which one of the following is true?

A
AA′ = 1
B
A = A-1
C
AB = BA
D
(AB)' = BA
Question 12 Explanation: 
Question 13

Backward Euler method for solving the differential equation dy/dx = f(x,y) is specified by, (choose one of the following).

A
yn+1 = yn + hf(xn, yn)
B
yn+1 = yn + hf(xn+1, yn+1)
C
yn+1 = yn-1 + 2hf(xn, yn)
D
yn+1 = (1 + h) f(xn+1, yn+1)
Question 13 Explanation: 
dy/dx = f(x,y)
With initial value y(x0) = y0. Here the function f and the initial data x0 and y0 are known. The function y depends on the real variable x and is unknown. A numerical method produces a sequence y0, y1, y2, ....... such that yn approximates y(x0 + nh) where h is called the step size.
→ The backward Euler method is helpful to compute the approximations i.e.,
yn+1 = yn + hf(x n+1, yn+1)
Question 14

Let A and B be any two arbitrary events, then, which one of the following is true?

A
P(A∩B) = P(A)P(B)
B
P(A∪B) = P(A) + P(B)
C
P(A|B) = P(A∩B)P(B)
D
P(A∪B) ≤ P(A) + P(B)
Question 14 Explanation: 
(A) Happens when A and B are independent.
(B) Happens when A and B are mutually exclusive.
(C) Not happens.
(D) P(A∪B) ≤ P(A) + P(B) is true because P(A∪B) = P(A) + P(B) - P(A∩B).
Question 15

The number of distinct simple graphs with upto three nodes is

A
15
B
10
C
7
D
9
Question 15 Explanation: 
Question 16

The tank of matrix is:

A
0
B
1
C
2
D
3
Question 16 Explanation: 
Question 17

Some group (G,o) is known to be abelian. Then, which one of the following is true for G?

A
g = g-1 for every g ∈ G
B
g = g2 for every g ∈ G
C
(goh)2 = g2oh2 for every g,h ∈ G
D
G is of finite order
Question 17 Explanation: 
Associate property of a group (aob)oc = ao(boc)
For Abelian group, commutative also holds
i.e., (aob) = (boa)
Consider option (C):
(goh)2 = (goh)o(gog)
= (hog)o(goh)
= (ho(gog)oh)
= ((hog2)oh)
= (g2oh)oh
= g2o(hoh)
= g2oh2 [True]
Question 18

In a compact single dimensional array representation for lower triangular matrices (i.e all the elements above the diagonal are zero) of size n × n, non-zero elements (i.e elements of the lower triangle) of each row are stored one after another, starting from the first row, the index of the (i, j)th element of the lower triangular matrix in this new representation is:

A
i + j
B
i + j - 1
C
j + i(i-1)/2
D
i + j(j-1)/2
Question 18 Explanation: 
Though not mentioned in question, from options it is clear that array index starts from 1 and not 0.
If we assume array index starting from 1 then, ith row contains i number of non-zero elements. Before ith row there are (i-1) rows, (1 to i-1) and in total these rows has 1+2+3......+(i-1) = i(i-1)/2 elements.
Now at ith row, the jth element will be at j position.
So the index of (i, j)th element of lower triangular matrix in this new representation is
j = i(i-1)/2
Question 19

The number of substrings (of all lengths inclusive) that can be formed from a character string of length n is

A
n
B
n2
C
n(n-1)/2
D
n(n+1)/2
Question 19 Explanation: 
No. of substrings of length
n = 1
(n-1) = 2
(n-2) = 3
So, Total = n(n+1)/2
Question 20

On the set N of non-negative integers, the binary operation __________ is associative and non-commutative.

A
fog
Question 20 Explanation: 
The most important associative operation that is not commutative is function composition. If you have two functions f and g, their composition, usually denoted fog, is defined by
(fog)(x) = f(g(x))
It is associative, (fog)oh = fo(goh), but its usually not commutative. fog is usually not equal to gof.
Note that if fog exists then gof might not even exists.
Question 21

Amongst the properties {reflexivity, symmetry, anti-symmetry, transitivity} the relation R = {(x,y) ∈ N2 | x ≠ y } satisfies __________.

A
symmetry
Question 21 Explanation: 
It is not reflexive as xRx is not possible.
It is symmetric as if xRy then yRx.
It is not antisymmetric as xRy and yRx are possible and we can have x≠y.
It is not transitive as if xRy and yRz then xRz need not be true. This is violated when x=x.
So, symmetry is the answer.
Question 22

The number of subsets {1, 2, ... n} with odd cardinality is __________.

A
2n-1
Question 22 Explanation: 
Total no. of subsets with n elements is 2n.
And so, no. of subsets with odd cardinality is half of total no. of subsets = 2n /n = 2n-1
Question 23

The number of edges in a regular graph of degree d and n vertices is _________.

A
d*n/2
Question 23 Explanation: 
Sum of degree of vertices = 2 × no. of edges
d * n = 2 * |E|
∴ |E| = d*n/2
Question 24

The probability of an event B is P1. The probability that events A and B occur together is P2 while the probability that A and occur together is P3. The probability of the event A in terms of P1, P2 and P3 is __________.

A
P2 + P3
Question 24 Explanation: 
P(A∩B') = P(A) - P(A∩B)
P3 = P(A) - P2
P(A) = P2 + P3
Question 25

Let A, B and C be independent events which occur with probabilities 0.8, 0.5 and 0.3 respectively. The probability of occurrence of at least one of the event is __________

A
0.93
Question 25 Explanation: 
P(A∪B∪C) = P(A) + P(B) + P(C) - P(A∩B) - P(B∩C) - P(A∩C) + P(A∩B∩C)
Since all the events are independent, so we can write
P(A∪B∪C) = P(A) + P(B) + P(C) - P(A)P(B) - P(B)P(C) - P(A)P(C) + P(A)P(B) P(C)
= 0.8 + 0.5 + 0.3 - 0.4 - 0.5 - 0.24 + 0.12
= 0.93
Question 26

The Hasse diagrams of all the lattices with up to four elements are __________ (write all the relevant Hasse diagrams).

A
Question 26 Explanation: 
For 1 element:
We can't draw lattice with 1 element.
For 2 element:

For 3 element:

For 4 element:
Question 27

Match the following items

A
(i) - (b), (ii) - (c), (iii) - (d), (iv) - (a)
Question 27 Explanation: 
Note: Out of syllabus.
Question 28

Find the inverse of the matrix

A
B
C
D
Question 28 Explanation: 
Using eigen values, the characteristic equation we get is,
-λ3 + 2λ2 - 2 = 0
Using Cayley-Hamiltonian theorem
-A3 + 2A2 - 2I = 0
So, A-1 = 1/2 (2A - A2)
Solving we get,
Question 29

Let p and q be propositions. Using only the truth table decide whether p ⇔ q does not imply p → q is true or false.

A
True
B
False
Question 29 Explanation: 

So, "imply" is False making "does not imply" True.
Question 30

(a) Let * be a Boolean operation defined as
If C = A * B then evaluate and fill in the blanks:
(i) A * A = _______
(ii) C * A = _______
(b) Solve the following boolean equations for the values of A, B and C:

A
Theory Explanation.
Question 31

A 3-ary tree is a tree in which every internal node has exactly three children. Use induction to prove that the number of leaves in a 3-ary tree with n interval nodes is 2(n-1)+3.

A
Theory Explanation.
Question 32

Every element a of some ring (R,+,0) satisfies the equation aoa = a.
Decide whether or not the ring is commutative.

A
Theory Explanation.
Question 33

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 33 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 34

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 34 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 35

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 35 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 36

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 36 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 37

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 37 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 38

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 38 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 39

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 39 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 40

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 40 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 41

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 41 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 42

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 42 Explanation: 

No. of edges = 4
Question 43

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 43 Explanation: 
From the given information we can write,
|Y||X| = 97
→ Option A only satisfies.
Question 44

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 44 Explanation: 
Rational number consists of number '0'. If 0 is present in a set inverse is not possible under multiplication.
Question 45

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 45 Explanation: 
1 - no. 6 on both dice
1 - (5/6 × 5/6) = 1 - (25/36) = 11/36
Question 46

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 46 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 47

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 47 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 48

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 48 Explanation: 
Question 49

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 49 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 50

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 50 Explanation: 
When x = F and y = F
then option (D) will be False.
There are 50 questions to complete.

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