Recent questions tagged discrete-maths - GATE CSE Doubts

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Gate overflow book
I am having a confusion in precedence order of logical operators. For e.g. consider the expression (a ∧ b) → (a ∧ c) ∨ d. Then how is the expression evaluated? Like is it ((a ∧ b) → (a ∧ c)) ∨ d or (a ∧ b) →((a ∧ c) ∨ d)? ... than implication, so the second one should be correct. But from the solution, I see it is the first one. Link to the question: https://gateoverflow.in/654

asked 11 hours ago in Mathematical Logic by hadarsh (5 points) | 7 views

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What is total number of planer graph can be formed with 6 vertices ?

asked 5 days ago in Graph Theory by subhadip997 (9 points) | 29 views

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TestBook Test Series
Consider G(V, E) be a complete undirected graph with 6 edges having a distinct weight from 1, 3, 9, 27, 81, and 243. Which of the following will NOT be the weight of them minimum spanning tree of G? (*This question may have multiple correct answers) A)121 B)13 C)40 D)31

asked Jan 1 in Graph Theory by nisargdoshi (7 points) | 35 views

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Made easy 2018 postal study course
Why is the answer is d)? I guess it should be a) can someone explain please

asked Dec 28, 2020 in Mathematical Logic by Anshul purohit (5 points) | 18 views

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how to prove function injective or not
Let A, B, and C be finite sets, and f : B to C and g : A to B be functions. Let h be the function with domain A and range C that maps x in A to f (g(x)). Prove or disprove the following claim: If h is injective, then g must be injective.

asked Dec 21, 2020 in Set Theory & Algebra by tyagiabhi (5 points) | 19 views

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#made-easy #discrete-maths
A group of 5 friends sitting on a bench. You have joined them with 8 sweets.All of you decided to share among ourself. The number of ways this distribution is possible is ___ i am getting ans 1287 but answer given is 20160 my approach is distribution of undistinguishable objects into distinguishable boxes. so formula is n+r-1Cr here n =6,r=8 so ans is 13C8

asked Dec 9, 2020 in Combinatory by 404 found (31 points) | 12 views

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#self-doubt #discrete-maths
can someone explains difference between equivalence classes and partitions. according to wiki Every element x of X is a member of the equivalence class [x]. Every two equivalence classes [x] and [y] are either equal or disjoint. ... below gate question https://gateoverflow.in/652/gate2000-2-5 they considers equivalence classes as partitions.Can someone explains why?

asked Nov 30, 2020 in Set Theory & Algebra by 404 found (31 points) | 18 views

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#dicrete-maths #made-easy
Let G be a group.Suppose that the number of elements in G of order 5 is 28.Determine the number of distinct subgroups of G of order 5 __. Ans -7 .can someone explains how?

asked Nov 28, 2020 in Set Theory & Algebra by 404 found (31 points) | 15 views

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#discrete-maths #made-easy
In a poset (A,<=) ,if there is no element ,x belongs to A with x<y then which of the following is true? An element x exists for which x=y. An element x is maximal in poset. A set with the same subset of poset An element x is ... correct bcz an element x is said to maximal if there exists no element y belongs to A such that xRy holds (x<y in this question).

asked Nov 28, 2020 in Set Theory & Algebra by 404 found (31 points) | 9 views

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#discrete-maths #made-easy
For sets A and B ,let f:A?B and g:B?A be functions such that f(g(x))=x for each x.which of the following options is/are true? The function f must be one to one. The function f must be onto The function g must be one to one the function g must be onto ans is b,c. can someone explains how?

asked Nov 28, 2020 in Set Theory & Algebra by 404 found (31 points) | 10 views

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Kenneth H Rosen
What is the meaning of all the four options? Please explain in detail.

asked Nov 27, 2020 in Mathematical Logic by Kindaichi (10 points) | 30 views

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Could not found the source
A)T B) F C) T D) F E) T F) T G) F H) T Are these truth values that I assigned correct?

asked Nov 21, 2020 in Mathematical Logic by Marwa-jami (5 points) | 22 views

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Kenneth h rosen 7th Edition chapter 2 section 2.5 "cardinality of sets"

asked Nov 21, 2020 in Set Theory & Algebra by ykrishnay (7 points) | 25 views

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Kenneth h rosen 7th Edition chapter 2 section 2.4 "Sequences and Summation"

asked Nov 20, 2020 in Set Theory & Algebra by ykrishnay (7 points) | 19 views

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A site on google
Which of the following formulas represents the sentence, 'Share prices will go up, and if interest rates go up too, there will be a recession', where; p means 'share prices will go up' q means 'interest rates will go up' r means 'there will be a recession'. A) (p ∧ q) →r B) p∧( q →r)

asked Nov 17, 2020 in Mathematical Logic by Marwa-jami (5 points) | 18 views

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BS Gerewal engineering mathematics
hey guys, what is meant by the statement- “cards are drawn in succession” . does it means whether one by one the cards were drawn OR all the cards were drawn at once any help is really appreciated….

asked Oct 29, 2020 in Probability by rish1602 (9 points) | 15 views

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Gatebook function
How to solve this type of question ?

asked Oct 2, 2020 in Set Theory & Algebra by Raj_81 (11 points) | 23 views

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NPTEL DISCRETE STRUCTURE ASSIGNMENT QUESTION
Which of the following are logical consequences of { ($\alpha$ → $\beta$’), $\beta$, ($\gamma$ ’ → $\alpha$) } ($\alpha$ → $\beta$’) $\beta$’ $\gamma$ $\alpha$ Answer given is C but if this question asked as MSQ question then can A be the possible answer??

asked Sep 19, 2020 in Mathematical Logic by Akanksha Agrawal (309 points) | 67 views

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Self doubt - Graph Connectivity (NPTEL & PY)
Let G be a graph with n vertices and if every vertex has a degree of at least $\frac{n−1}{2}$ then G is connected. Source : https://gateoverflow.in/1221/gate2007-23 Let G be a graph with n vertices and if every vertex has a degree of at ... then G is connected. source : https://nptel.ac.in/courses/106/106/106106183/ My doubt : Which one is right?

asked Sep 17, 2020 in Graph Theory by KUSHAGRA गुप्ता (1.4k points) | 50 views

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Self Doubt - Planar graph (PY)
$K_5$ is non-planar. I am showing you my proof. Please tell me whether this is the right way or not to prove that $K_5$ is non-planar. $\sum$ (deg)$=4+4+4+4+4=20$ $e=10$ and $n=5$ Assume $K_5$ is planar. $v-e+r=2$ ... $K_5$ is non-planar. If this is the right way, why this method didn't work in this graph. Source: https://gateoverflow.in/87129/gate1990-3-vi

asked Sep 15, 2020 in Graph Theory by KUSHAGRA गुप्ता (1.4k points) | 33 views

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KENNETH ROSEN DISCRETE MATHEMATICS PAGE 432 Q11
How many ways are there to chose eight coins from piggy bank containing 100 identical pennies and 80 identical nickels.

asked Sep 14, 2020 in Combinatory by StoneHeart (735 points) | 75 views

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LATTICE ASSOCIATIVITY DOUBT
I wasn't convinced about the associativity property of lattices, and the proof i found on math.stackexchange seemed reasonable, but still i couldnt wrap my head around it. I tried to make a counter example, and in the above diagram (b join c) ... otherwise it would've satisfied associativity. But i cant seem to figure out why this diagram isn't a lattice. Please help.

asked Aug 22, 2020 in Set Theory & Algebra by rish-18 (9 points) | 59 views

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Self Doubt in Propositional Logic
Translate this English proposition to Logical expression : “you will not get an A grade unless you work hard”

asked Aug 21, 2020 in Mathematical Logic by AbhayPrajapati (7 points) | 36 views

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ISI CSB 2018
State, with justification, which of the following expressions f, g and h, define valid real-valued functions over the set of positive rational numbers. We denote a rational number by m/n, where m and n are positive integers. (a) f(m/n) = 2^m − 2^n. (b) g(m/n) = log m − log n. (c) h(m/n) = (m^2 − n^2)/(mn).

asked Aug 20, 2020 in Set Theory & Algebra by suparna kar (9 points) | 31 views

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K Rosen(7th ed). Chapter 6. Exercise 6.4. Q.17.
Question: Answer 1: Answer 2: I am not able to understand the solution.What’s happening here? Please help.

asked Aug 13, 2020 in Combinatory by RasMalai (27 points) | 30 views

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Self-Doubt 10 couple, { 10 men and 10 women }, Number of Ways

asked Aug 12, 2020 in Combinatory by mamtuj (-25 points) | 59 views

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ISI CSB 2018
Given A = {1, 2, 3, .... , 70}, show that for any six elements a1, a2, a3, a4, a5 and a6 belonging to A, there exists one pair ai and aj for which |ai − aj| ≤ 14 (i not equals to j).

asked Aug 11, 2020 in Set Theory & Algebra by suparna kar (9 points) | 29 views

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Combinatorics and Probability
Six people, including A,B, and C, form a queue in a random order (all 6! orderings are equiprobable). Consider the event "B is between A and C in the queue". What is its probability? (The order of A and C can be arbitrary, but B should be between them).

asked Aug 5, 2020 in Probability by aryashah2k (2 points) | 32 views

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Combinatorics and Probability
Six people including A,B, and C, form a queue in a random order (all 6! orderings are equiprobable). Consider the event "A precedes B in the queue". (Again this event does not mention C or other people in the queue. It happens when A is ... not require that B is the next after A, some people could be between A and B.) What is the probability of this event?

asked Aug 5, 2020 in Probability by aryashah2k (2 points) | 237 views

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Self Doubt : Lattice
$\left \{ 1,2,3,24,30 \right \}$ is it a lattice? I think this poset has no lub as $24$ and $30$ are not comparable. Am I right?

asked Jul 20, 2020 in Set Theory & Algebra by srestha (1k points) | 73 views

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Relation :DiscreteMath-GB
Let R be a relation from a set A to a set B. The inverse relation from B to A, denoted by , is the set of ordered pairs . S1: R is reflexive relation iff S2: R is a symmetric relation iff Which one of the following statements is true? (A).Only S1 (B).Only S2 (C).Both S1 and S2 (D).None

asked Jul 10, 2020 in Set Theory & Algebra by srestha (1k points) | 71 views

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PROBABILTY AND DISTRIBUTIONS
A elevator manufacturing company believes that 'X' is the amount of that can elevator withstand without any damage with is mean 100 and standard deviation 10. This elevator is used to lift the company staff persons with mean 5 and standard deviation 0.5. How many staff person would have to be in the elevator for the probability of No damage exceeds to 0.85.

asked Jun 30, 2020 in Mathematical Logic by Stanfordboi (5 points) | 14 views

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Graph Theory with Applications to Engineering and Computer Science, Narsingh Deo, Chapter 4 Question 27

asked Jun 23, 2020 in Graph Theory by dararirum (5 points) | 44 views

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Graph Theory with Applications to Engineering and Computer Science, Narsingh Deo, Chapter 2 Question 21

asked Jun 23, 2020 in Others by dararirum (5 points) | 44 views

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Expectation : Self Doubt
There is a bag containing 5 white and 5 black balls. You repeat the following experiment till you see a white ball : take a ball uniformly at random out of the bag. If it is white, stop. Otherwise, put it back in the bag. What is the expected number of times you will need to draw a ball from the bag ?

asked Jun 19, 2020 in Probability by suparna kar (9 points) | 154 views

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Combinatorics Simple doubt
What is the difference between flipping a pair of Distinct dices and flipping a pair of Identical Dices ??

asked Jun 18, 2020 in Mathematical Logic by BHASHKAR (73 points) | 24 views

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Self doubt GRAPH THEORY

asked May 31, 2020 in Graph Theory by Abhipsa (5 points) | 31 views

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self doubt permutation and combination

asked May 31, 2020 in Combinatory by Abhipsa (5 points) | 19 views

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Self Doubt recurrence equation

asked May 31, 2020 in Combinatory by Abhipsa (5 points) | 29 views

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P&C - self doubt
Find the number of arrangements of the letters of the word "INDEPENDENCE" if they start with "P" and end with "D"

asked May 27, 2020 in Combinatory by Abhipsa (5 points) | 25 views

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