Recent questions and answers in Combinatory - GATE CSE Doubts

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TIFR-GS2021 Question
A box contains 5 red marbles, 8 green marbles, 11 blue marbles, and 15 yellow marbles. We draw marbles uniformly at random without replacement from the box. What is the minimum number of marbles to be drawn to ensure that out of the marbles drawn, at least 7 are of the same colour? (A) 7 (B) 8 (C) 23 (D) 24 (E) 39

answered Mar 24 in Combinatory by zxy123 (3.6k points) | 10 views

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TIFR-GS2021 Question
Let $d$ be the number of positive square integers (that is, it is a square of some integer) that are factors of $20^5\times21^5$. Which of the following is true about $d$? (A) $50 \leq d < 100$ (B) $100 \leq d < 150$ (C) $150 \leq d < 200$ (D) $200 \leq d < 300$ (E) $300 \leq d$

asked Mar 24 in Combinatory by zxy123 (3.6k points) | 5 views

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TIFR-GS2021 Question
Let $n$, $m$ and $k$ be three positive integers such that $n \geq m \geq k$. Let $S$ be a subset of $\{1, 2, , n\}$ of size $k$. Consider sampling a function uniformly at random from the set of all functions mapping $\{1, , n\}$ to $\{1, , m\}$. What is the probability ... $1 - \frac{k!{n\choose k}}{n^k}$ (E) $1 - \frac{k!{n\choose k}}{m^k}$

asked Mar 24 in Combinatory by zxy123 (3.6k points) | 4 views

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NPTEL Assignment
In how many ways can one arrange five 1’s and five -1’s so that all ten partial sums (starting with the first summand) are nonnegative?

asked Feb 6 in Combinatory by Kindaichi (10 points) | 23 views

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Kenneth H rosen Chapter 6 - "Counting" Section 6.4

asked Jan 20 in Combinatory by ykrishnay (7 points) | 17 views

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Gate Applied Course Test Series
There are 20 intermediate stops on a route of a transport corporation bus. The number of ways in which the bus can stop at 6 of these intermediate stops such that no 2 stops are consecutive is ?

answered Jan 12 in Combinatory by zxy123 (3.6k points) | 33 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 (37 points) | 13 views

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Self Doubt. Combinatorics. How do I solve this question

answered Nov 11, 2020 in Combinatory by SarathBaswa (849 points) | 50 views

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Self Doubt in distribution problem
I have a small doubt which is :- Is identical to identical distribution the same as integer partition? Or in general, how to deal with distribution of identical letters to identical boxes?

asked Nov 9, 2020 in Combinatory by s_dr_13 (15 points) | 16 views

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Made easy - Discrete mathematics
How many ways can 10 balls be chosen from a container having 10 identical green balls , 5 identical yellow balls and 3 identical blue balls

answered Oct 30, 2020 in Combinatory by ijnuhb (747 points) | 112 views

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online search
there are 5 pairs of different shoes.in how many ways can each person so that at least two person get a complete pair

asked Oct 20, 2020 in Combinatory by ajay05908 (5 points) | 14 views

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Rosen - combinatorics ex 5.5 que 4
Every day a student randomly chooses a sandwich for lunch from a pile of wrapped sandwiches. If there are six kinds of sandwiches how many diff ways are there for the student to choose sandwiches for the 7 days of a week if the order in which sandwiches are chosen matters

answered Oct 17, 2020 in Combinatory by mayureshpatle (861 points) | 27 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.

answered Oct 9, 2020 in Combinatory by Nikhil_dhama (151 points) | 93 views

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Applied scholarship test
The number of straight lines that can be drawn through 90 points.Given that 10 of them lie on a straight line.

answered Sep 28, 2020 in Combinatory by himanshu2021 (133 points) | 39 views

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Applied Scholarship Test
A)1/16 B)1/15 C)1/4 D)NONE

answered Sep 28, 2020 in Combinatory by himanshu2021 (133 points) | 30 views

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Test Question of Applied Gate
Not able to solve this question. How to solve this type of questions?

answered Sep 16, 2020 in Combinatory by Ehraz Hasan (366 points) | 42 views

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3 answers

Rosen-Chapter 8, Ex 8.5,Question 24
Find the probability that when a fair coin is flipped five times tails comes up exactly three times, the first and last flips come up tails, or the second and fourth flips come up heads.

answered Sep 16, 2020 in Combinatory by ijnuhb (747 points) | 121 views

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Self doubt on Permutations and combination
If no three diagonals of a convex decagon meet at the same point inside the decagon, into how many line segments are the diagonals divided by their intersection?

asked Sep 9, 2020 in Combinatory by ijnuhb (747 points) | 31 views

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Self Doubt on Combinatorics
Why these 2 questions solved in different manner while it seems like both are same type questions?? Anyone Please.

asked Sep 4, 2020 in Combinatory by AbhayPrajapati (7 points) | 25 views

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self doubt o this question
How can you get like for 2 I’s (3!*4)/2! ?? I know i am asking such a basic question but i’m little bit confused that’s why i asking.

asked Sep 4, 2020 in Combinatory by AbhayPrajapati (7 points) | 21 views

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Self Doubt on Combinatorics
Is there any difference between these 2 questions?? If yes then how can we solve this???

answered Sep 3, 2020 in Combinatory by ijnuhb (747 points) | 62 views

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Allan Career Institute: Discrete Math
Let $f\left ( x\right )$ be continuous probability density function of a random variable $X.$ Then probability of $a\leq X< b$ is $A)f\left ( b \right )-f\left ( a \right )$ $B)f\left ( a-b \right )$ $C)\int_{b}^{a}xf\left ( x \right )dx$ $D)\int_{b}^{a}f\left ( x \right )dx$ Plz give some link for probability of pdf

answered Aug 16, 2020 in Combinatory by jayeshasawa001 (2.5k points) | 76 views

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Self Doubt recurrence equation

answered Aug 16, 2020 in Combinatory by Arkaprava (801 points) | 31 views

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Kenneth Rosen(7th ed). Chapter 6. Example 16.
Each user on a computer system has a password, which is six to eight characters long, where each character is an uppercase letter or a digit. Each password must contain at least one digit. How many possible passwords are there? Answer is given in book as : P^6 + P ... on for P^7 and P8. My question is why can't we calculate P^6 like 36^5 * C(6,1) * 10 ?

answered Aug 15, 2020 in Combinatory by Arkaprava (801 points) | 25 views

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Self Doubt. Combination, Circular. A, B, C, D, E, f are on circlular table.

answered Aug 14, 2020 in Combinatory by jayeshasawa001 (2.5k points) | 56 views

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2 answers

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

answered Aug 14, 2020 in Combinatory by jayeshasawa001 (2.5k points) | 59 views

+1 vote

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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.

answered Aug 13, 2020 in Combinatory by Arkaprava (801 points) | 31 views

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nptel assignment
I am getting answer 64 didn’t know how answer is 40

answered Aug 12, 2020 in Combinatory by Arkaprava (801 points) | 85 views

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#discrete mathematics #exponential generating function

answered Aug 12, 2020 in Combinatory by Arkaprava (801 points) | 19 views

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jee practice ques permutation
There are 5 apples 10 mangoes and 15 oranges in a basket. Then find number of ways of distributing 15 fruits each to 2 persons. a)56 b)64 c)66 d)72

answered Aug 11, 2020 in Combinatory by Arkaprava (801 points) | 39 views

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Made easy topic wise tests
please explain this briefly!! .

answered Aug 11, 2020 in Combinatory by jayeshasawa001 (2.5k points) | 37 views

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Explain this briefly
2^n 2^n-1 (2^n-1)-1 n^2

answered Aug 10, 2020 in Combinatory by jayeshasawa001 (2.5k points) | 53 views

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Recurrence relation - ROSEN
$1.\ a_{k}=3a_{k-1}+4^{k-1}| a_{0}=1$ $2.\ a_{k}=4a_{k-1}-4_{k-2}+k^2| a_{0}=2,a_{1}=5$

asked Aug 6, 2020 in Combinatory by KUSHAGRA गुप्ता (1.4k points) | 69 views

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Self doubt on combinatorics
How many strings are there, using 10 A's, 12 B's, 11 C's, and 15 D's, such that no A is followed by a B, and no C is followed by a D?

asked Jul 29, 2020 in Combinatory by RasMalai (27 points) | 16 views

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Sheldon Ross (8th ed). Chapter 1. Self test problems. Q 4.

asked Jul 29, 2020 in Combinatory by RasMalai (27 points) | 36 views

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Sheldon Ross(8th ed). Chapter 1. Theoretical Excercises. Q 11.

asked Jul 27, 2020 in Combinatory by RasMalai (27 points) | 41 views

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self doubt permutation and combination

answered Jun 1, 2020 in Combinatory by vps123 (9 points) | 22 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"

answered May 29, 2020 in Combinatory by Mohit Kumar 6 (5 points) | 33 views

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ISI Tomato Book
The value of $\sum \binom{k}{i} \binom{M-k}{100-i} [(k-i)/(M-100)]/ \binom{M}{100}$, where M – k > 100, k > 100 and $\binom{m}{n}$= m!/{(m – n)!n!} equals (summation running from i = 0 to i = 100) (a) k/M (b) M/k (c)$k/M^{2}$ (d) $M/k^{2}$

asked May 13, 2020 in Combinatory by PSDesai09 (5 points) | 22 views

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GATE2018-46 Video Solution
The number of possible min-heaps containing each value from $\{1,2,3,4,5,6,7\}$ exactly once is _______

asked Apr 18, 2020 in Combinatory by admin (573 points) | 15 views

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