Discrete Mathematics and Its Applications ( 8th International Edition ) ISBN:9781260091991
Discrete Mathematics and Its Applications ( 8th International Edition ) ISBN:9781260091991
8th Edition
ISBN: 9781259676512
Author: Kenneth H Rosen
Publisher: McGraw-Hill Education
bartleby

Concept explainers

Permutations and Combinations
If there are 5 dishes, they can be relished in any order at a time. In permutation, it should be in a particular order. In combination, the order does not matter. Take 3 letters a, b, and c. The possible ways of pairing any two letters are ab, bc, ac, ba…
Counting Theory
The fundamental counting principle is a rule that is used to count the total number of possible outcomes in a given situation.
bartleby

Videos

Textbook Question
Book Icon
Chapter 6.5, Problem 22E

w many ways can an airplane pilot be scheduled for five days of flying in October if he cannot work on consecutive days?

Expert Solution & Answer
Check Mark

Want to see the full answer?

Check out a sample textbook solution
Blurred answer
Previous
Chapter 6.5, Problem 21E
Next
Chapter 6.5, Problem 23E

Chapter 6 Solutions

Discrete Mathematics and Its Applications ( 8th International Edition ) ISBN:9781260091991

Ch. 6.1 - There are 18 mathematics majors and 325 computer...Ch. 6.1 - An office building contains 27 floors and has 37...Ch. 6.1 - A multiple-choice test contains 10 questions....Ch. 6.1 - A particular of shirt comes in 12 colors, has a...Ch. 6.1 - Six different fly from New York to Denver and...Ch. 6.1 - There are four major auto routes from Boston to...Ch. 6.1 - How many different three-letter initials can...Ch. 6.1 - How many different three-letter initials with none...Ch. 6.1 - How many different three-letter initials are there...Ch. 6.1 - How many bit strings are there of length eight?
Ch. 6.1 - How many bit strings of length ten both begin and...Ch. 6.1 - How many bit strings are there of length six or...Ch. 6.1 - How many bit strings with length not exceeding n,...Ch. 6.1 - How many bit strings of lengthn,wherenis a...Ch. 6.1 - How many strings are there of lowercase letters of...Ch. 6.1 - How many strings are there of four lowercase...Ch. 6.1 - How many strings of five ASCII characters @ (“at”...Ch. 6.1 - How many 5-element DNA sequences end with A? start...Ch. 6.1 - lg.How many 6-element RNA sequences Do not contain...Ch. 6.1 - How many positive integers between 5 and 31 are...Ch. 6.1 - How many positive integers between 50 and 100 are...Ch. 6.1 - How many positive integers less than 1000 are...Ch. 6.1 - How many positive integers between 100 and 999...Ch. 6.1 - How many positive integers between 1000 and 9999...Ch. 6.1 - How many strings of three decimal digits do not...Ch. 6.1 - How many strings of four decimal digits do not...Ch. 6.1 - Prob. 27ECh. 6.1 - How many license, plates can be made using either...Ch. 6.1 - How many license plates can be made using either...Ch. 6.1 - How many license plates can be made using either...Ch. 6.1 - How many license plates can be made using either...Ch. 6.1 - How many strings of eight uppercase English...Ch. 6.1 - How many strings of eight English letters are...Ch. 6.1 - Prob. 34ECh. 6.1 - How many one-to-one functions are there from a set...Ch. 6.1 - How many functions are there from the set {1,2,n},...Ch. 6.1 - Prob. 37ECh. 6.1 - How many partial functions (seeSection 2.3)are...Ch. 6.1 - Prob. 39ECh. 6.1 - Prob. 40ECh. 6.1 - Prob. 41ECh. 6.1 - How many 4-element DNA sequences do not contain...Ch. 6.1 - How many 4-eJement RNA sequenoes contain the base...Ch. 6.1 - On each of the 22 work days in a particular month,...Ch. 6.1 - At a large university, 434 freshman, 883...Ch. 6.1 - Prob. 46ECh. 6.1 - How many ways are there to seat six people around...Ch. 6.1 - In how many ways can a photographer at a wedding...Ch. 6.1 - In how many ways can a photographer at a wedding...Ch. 6.1 - How many bit strings of length seven either begin...Ch. 6.1 - Prob. 51ECh. 6.1 - How many bit strings of length 10 contain either...Ch. 6.1 - How many bit strings of length eight contain...Ch. 6.1 - ...Ch. 6.1 - Prob. 55ECh. 6.1 - Prob. 56ECh. 6.1 - Suppose that a password for a computer system must...Ch. 6.1 - The name, of a variable in the C programming...Ch. 6.1 - The name of a variable in the JAVA programming...Ch. 6.1 - 6o, The International Telecommunications Union...Ch. 6.1 - Prob. 61ECh. 6.1 - A key in the Vigenere cryptosystem is a string of...Ch. 6.1 - Prob. 63ECh. 6.1 - Suppose that P and q are prime numbers and than n...Ch. 6.1 - Use the principle of inclusion-exclusion to find...Ch. 6.1 - Prob. 66ECh. 6.1 - Prob. 67ECh. 6.1 - Prob. 68ECh. 6.1 - Prob. 69ECh. 6.1 - Prob. 70ECh. 6.1 - Prob. 71ECh. 6.1 - Determine the number of matches played in a...Ch. 6.1 - Prob. 73ECh. 6.1 - *74-Use the product rule to show that there are 22...Ch. 6.1 - Prob. 75ECh. 6.1 - Use mathematical induction to prove the product...Ch. 6.1 - Prob. 77ECh. 6.1 - Prob. 78ECh. 6.2 - Prob. 1ECh. 6.2 - Show that if there are 30 students in a class,...Ch. 6.2 - A drawer contains a dozen brown socks and a dozen...Ch. 6.2 - Abowl contains 10 red balls and 10 blue balls....Ch. 6.2 - Undergraduate students at a college belong to one...Ch. 6.2 - 6,There are six professors teaching the...Ch. 6.2 - group of five (not necessarily consecutive)...Ch. 6.2 - 8,Let d be a positive integer, Show that among anv...Ch. 6.2 - Letnbe a positive integer. Show that in any set...Ch. 6.2 - Prob. 10ECh. 6.2 - Prob. 11ECh. 6.2 - Prob. 12ECh. 6.2 - Prob. 13ECh. 6.2 - Prob. 14ECh. 6.2 - Show that if five integers are selected from the...Ch. 6.2 - i6. Show that if seven integers are selected from...Ch. 6.2 - How many numbers must be selected from the set...Ch. 6.2 - Howmany numbers must be selected from the set...Ch. 6.2 - A company stores products in a warehouse. Storage...Ch. 6.2 - Suppose that there are nine students in a discrete...Ch. 6.2 - i. Suppose that every student in a discrete...Ch. 6.2 - Prob. 22ECh. 6.2 - Construct a sequenceof16 positive integers that...Ch. 6.2 - Prob. 24ECh. 6.2 - Show that whenever 25 girl? and 25 boys are seated...Ch. 6.2 - Prob. 26ECh. 6.2 - Descnbe an algorithm in pseudocode for producing...Ch. 6.2 - Prob. 28ECh. 6.2 - Prob. 29ECh. 6.2 - Prob. 30ECh. 6.2 - Prob. 31ECh. 6.2 - Prob. 32ECh. 6.2 - Prob. 33ECh. 6.2 - Prob. 34ECh. 6.2 - In the 17th century, there were more than 800,000...Ch. 6.2 - Prob. 36ECh. 6.2 - Prob. 37ECh. 6.2 - Prob. 38ECh. 6.2 - A computer network consists of six computers, Each...Ch. 6.2 - Prob. 40ECh. 6.2 - Prob. 41ECh. 6.2 - Prob. 42ECh. 6.2 - Ad arm wrestler is the champion for a period of 75...Ch. 6.2 - Prob. 44ECh. 6.2 - Prob. 45ECh. 6.2 - ,There are 51 houses on a street, Each house has...Ch. 6.2 - Letibe an irrational number, Showthatfor some...Ch. 6.2 - Prob. 48ECh. 6.2 - Prob. 49ECh. 6.3 - i. List all the permutations of{a, b,c}.Ch. 6.3 - How many different permutations are there of the...Ch. 6.3 - How many permutations of{a, b,c, d,e.fg]end withCh. 6.3 - LetS = {i,2, 3,4, 5}. List all the 3-permutations...Ch. 6.3 - Find the value of each of these quantities P(6,3)...Ch. 6.3 - Find the value of each of these quantities. CCs,i)...Ch. 6.3 - Find the number of 5-permutations of a set Kith...Ch. 6.3 - In how many different orders can five runners...Ch. 6.3 - Prob. 9ECh. 6.3 - There are six different candidates for governor of...Ch. 6.3 - ii.How many bit strings of length 10 contain...Ch. 6.3 - IE.How many bit strings of length12contain exactly...Ch. 6.3 - A group contains n men and n women. How many ways...Ch. 6.3 - Prob. 14ECh. 6.3 - Prob. 15ECh. 6.3 - Prob. 16ECh. 6.3 - Prob. 17ECh. 6.3 - Prob. 18ECh. 6.3 - Prob. 19ECh. 6.3 - Prob. 20ECh. 6.3 - Prob. 21ECh. 6.3 - Prob. 22ECh. 6.3 - Prob. 23ECh. 6.3 - Prob. 24ECh. 6.3 - Prob. 25ECh. 6.3 - Prob. 26ECh. 6.3 - Prob. 27ECh. 6.3 - Prob. 28ECh. 6.3 - Prob. 29ECh. 6.3 - Prob. 30ECh. 6.3 - Prob. 31ECh. 6.3 - Prob. 32ECh. 6.3 - Prob. 33ECh. 6.3 - Prob. 34ECh. 6.3 - Prob. 35ECh. 6.3 - Prob. 36ECh. 6.3 - Prob. 37ECh. 6.3 - Prob. 38ECh. 6.3 - Prob. 39ECh. 6.3 - Prob. 40ECh. 6.3 - Prob. 41ECh. 6.3 - Find the number of circular 3-permutations...Ch. 6.3 - Prob. 43ECh. 6.3 - Prob. 44ECh. 6.3 - How many ways are there for a horse race with...Ch. 6.4 - Find the expansion of (r + using combinatorial...Ch. 6.4 - Find the expansion of Cr + j,)5 using...Ch. 6.4 - Find the expansionCh. 6.4 - Find the coefficient of in Cr + y)13.Ch. 6.4 - How many terms are therein the expansion of...Ch. 6.4 - What isthecoefficient of .v in (1 +1)Ch. 6.4 - What is the coefficient of i9 in (2 - 1)Ch. 6.4 - What is the coefficient ofxsy9 in the expansion of...Ch. 6.4 - What is the coefficient of xloly" in the expansion...Ch. 6.4 - Prob. 10ECh. 6.4 - Prob. 11ECh. 6.4 - IS. Use the binomial theorem to find the...Ch. 6.4 - *3-Use the binomial theorem to find the...Ch. 6.4 - Give a formula for the coefficient ofi^in the...Ch. 6.4 - Prob. 15ECh. 6.4 - The row of Pascal’s triangle containing the...Ch. 6.4 - What is the r ow of Pascal's triangle containing...Ch. 6.4 - Prob. 18ECh. 6.4 - Prob. 19ECh. 6.4 - so. Use Exercise 18 andCorollary 1to show that...Ch. 6.4 - Prob. 21ECh. 6.4 - Suppose thatbis an integer withb> 7. Use the...Ch. 6.4 - Prove Pas cal’s identity, u sing the formula for...Ch. 6.4 - Suppose that t andnare integers withi which...Ch. 6.4 - Provethatifnandfcareintegers^th i< fc using a...Ch. 6.4 - Prove the identity (")(') = (J)(Xf), whenever n,...Ch. 6.4 - Prob. 27ECh. 6.4 - Prob. 28ECh. 6.4 - Letnbe a positive integer. Show thatCh. 6.4 - Prob. 30ECh. 6.4 - Prove the hockey-stick identity ('?’)...Ch. 6.4 - Show that if ra is a positive integer, then =2t" i...Ch. 6.4 - Prob. 33ECh. 6.4 - Prob. 34ECh. 6.4 - Prob. 35ECh. 6.4 - Prove the binomial theorem using mathematical...Ch. 6.4 - In this exercise we will count the number of paths...Ch. 6.4 - Prob. 38ECh. 6.4 - Prob. 39ECh. 6.4 - Prob. 40ECh. 6.4 - Prob. 41ECh. 6.4 - Prob. 42ECh. 6.4 - Determine a formula involving binomial...Ch. 6.5 - In how many different wavs can five elements be...Ch. 6.5 - Prob. 2ECh. 6.5 - Prob. 3ECh. 6.5 - Prob. 4ECh. 6.5 - Prob. 5ECh. 6.5 - Prob. 6ECh. 6.5 - Prob. 7ECh. 6.5 - How many different ways are there to choose a...Ch. 6.5 - A bagel shop has onion bagels, poppy seed bagels,...Ch. 6.5 - io. A croissant shop has plain croissants, cherry...Ch. 6.5 - ii. Howmany ways are there to choose eight coins...Ch. 6.5 - Homy different combinations of pennies, nickels,...Ch. 6.5 - Prob. 13ECh. 6.5 - How many solutions are there to the equation -T| +...Ch. 6.5 - How many solutions are there to the equation -T |...Ch. 6.5 - i6. How many solutions are there to the equation...Ch. 6.5 - strings of 10 ternary digits (o, 1. or 2) are...Ch. 6.5 - ,How many strings of 20-decima] digits are there...Ch. 6.5 - Prob. 19ECh. 6.5 - How many solutions are there to the inequality .ii...Ch. 6.5 - i. A Swedish tour guide has devised a clever way...Ch. 6.5 - w many ways can an airplane pilot be scheduled for...Ch. 6.5 - How many ways are there to distribute six...Ch. 6.5 - How many ways are there to distribute 12...Ch. 6.5 - Howmany wavs aiethereto distribute 12...Ch. 6.5 - Prob. 26ECh. 6.5 - How many positive integers less than 1,000,000...Ch. 6.5 - a8. How many positive integers less than 1,000,000...Ch. 6.5 - Prob. 29ECh. 6.5 - Prob. 30ECh. 6.5 - Prob. 31ECh. 6.5 - How many different strings can be made from the...Ch. 6.5 - How many different strings can be made from the...Ch. 6.5 - different strings can be made from the letters...Ch. 6.5 - How many different strings can be made from the...Ch. 6.5 - How many strings idth five or more characters can...Ch. 6.5 - How many strings with seven or more characters can...Ch. 6.5 - How many different bit strings can be formed using...Ch. 6.5 - Prob. 39ECh. 6.5 - Prob. 40ECh. 6.5 - i....Ch. 6.5 - Prob. 42ECh. 6.5 - How many ways are. there to deal hands of seven...Ch. 6.5 - In bridge. the 52 cards of a standard deck are...Ch. 6.5 - How many ways are there to deal hands of five...Ch. 6.5 - , In how many ways can a dozen books be placed on...Ch. 6.5 - How many ways cannbooks be placed on t...Ch. 6.5 - Prob. 48ECh. 6.5 - Prob. 49ECh. 6.5 - Prob. 50ECh. 6.5 - Prob. 51ECh. 6.5 - How many ways are there to distribute five...Ch. 6.5 - Prob. 53ECh. 6.5 - 54-How many ways are there to put five temporary...Ch. 6.5 - Prob. 55ECh. 6.5 - Prob. 56ECh. 6.5 - Prob. 57ECh. 6.5 - 8,Howmany ways are thereto pack eightidentical...Ch. 6.5 - Prob. 59ECh. 6.5 - 6o. How many ways are there to distribute five...Ch. 6.5 - 6i. How many ways are there to distribute five...Ch. 6.5 - Suppose that a basketball league has 32 teams,...Ch. 6.5 - f 63. Suppose that a weapons inspector must...Ch. 6.5 - Howmanv dififerentterms are therein the expansion...Ch. 6.5 - Prob. 65ECh. 6.5 - Prob. 66ECh. 6.5 - Find the coefficient ofi3y2z5 in Qc + y + z)Ch. 6.5 - How many terms are there in the expansionCh. 6.6 - ...Ch. 6.6 - ...Ch. 6.6 - Prob. 3ECh. 6.6 - Prob. 4ECh. 6.6 - Find the next larger permutation in lexicographic...Ch. 6.6 - Find the next larger permutation in lexicographic,...Ch. 6.6 - Use Algorithm 1 to generate the 24 permutations of...Ch. 6.6 - Prob. 8ECh. 6.6 - Use Algorithm 3 to listallthe 3-combinations of{1,...Ch. 6.6 - Show that Algorithm1produces the next larger...Ch. 6.6 - Show that Algorithm 3 produces the next larger...Ch. 6.6 - Develop an algorithm for generating the...Ch. 6.6 - List all 3-permutations of {1,2,3,4,5}. The...Ch. 6.6 - Find the Cantor digits an ti2,that correspond to...Ch. 6.6 - Prob. 15ECh. 6.6 - i6,Find the permutations of {1,2,3,4,5} that...Ch. 6.6 - Prob. 17ECh. 6 - Explain how the sum and product rules can be used...Ch. 6 - Explain how to find the number of bit strings of...Ch. 6 - Prob. 3RQCh. 6 - How can yon find the number of possible outcomes...Ch. 6 - How can you find the number of bit strings...Ch. 6 - State the pigeonhole principle, Explain how the...Ch. 6 - State the generalized pigeonhole principle....Ch. 6 - ft What is the difference between an r-combination...Ch. 6 - What i s Pas cal's tri angle? How can arow of...Ch. 6 - What is meant by a combinatorial proof of an...Ch. 6 - ii. Explain how to prove Pascal's identity using a...Ch. 6 - Stateth e bin omial th eor em. Explain how to pr o...Ch. 6 - Explain how to find a formula for the number of...Ch. 6 - Letnand r be positive integers. Explain why the...Ch. 6 - Prob. 15RQCh. 6 - Prob. 16RQCh. 6 - a) How many ways are there to deal hands of five...Ch. 6 - Describe an algorithm for generating all the...Ch. 6 - i. How many ways are there to choose 6 items from...Ch. 6 - a.H 01 v many ways ar e ther e to ch o o se1o...Ch. 6 - Prob. 3SECh. 6 - How many strings of length10either start with ooo...Ch. 6 - Prob. 5SECh. 6 - Prob. 6SECh. 6 - Prob. 7SECh. 6 - Hoi v many positive integers less than iqoo have...Ch. 6 - Prob. 9SECh. 6 - Prob. 10SECh. 6 - Prob. 11SECh. 6 - How many people are needed to guarantee that at...Ch. 6 - Show that given anv set of 10 positive integers...Ch. 6 - Prob. 14SECh. 6 - Prob. 15SECh. 6 - Prob. 16SECh. 6 - Show that in a sequence ofmintegers there exists...Ch. 6 - Prob. 18SECh. 6 - Show that the decimal expansion of a rational...Ch. 6 - Once a computer worm infects a personal computer...Ch. 6 - si.How many ways are there to choose a dozen...Ch. 6 - ss.Findn if P(n,2] = 110. J\?i, n] = 5040....Ch. 6 - Prob. 23SECh. 6 - Show that ifnandrare nonnegative integers and n >...Ch. 6 - Prob. 25SECh. 6 - Give a combinatorial proof ofCorollary 2ofSection...Ch. 6 - Prob. 27SECh. 6 - a8. Prove using mathematical induction that O>• 2)...Ch. 6 - Prob. 29SECh. 6 - Show that V7' XIt. I = (’) if nis an integer withCh. 6 - Prob. 31SECh. 6 - Prob. 32SECh. 6 - How many bit strings of length n, where n > 4,...Ch. 6 - Prob. 34SECh. 6 - Prob. 35SECh. 6 - Prob. 36SECh. 6 - How many ways are there to assign 24 students to...Ch. 6 - Prob. 38SECh. 6 - - How many solutions are there to the equation xt...Ch. 6 - How many different strings can be made from the...Ch. 6 - How many subsets of a set with ten el e m ents...Ch. 6 - Prob. 42SECh. 6 - Prob. 43SECh. 6 - How many ways are. there to seat six boys and...Ch. 6 - How many ways are there to distribute six objects...Ch. 6 - How many ways are there to distribute five obj...Ch. 6 - Find these signless Stirling numb er s of the...Ch. 6 - Show that ifnis a positive integer, then ,Ch. 6 - Prob. 49SECh. 6 - Prob. 50SECh. 6 - Prob. 51SECh. 6 - j2, How many n-element RXA sequences consist of 4...Ch. 6 - *53. Suppose that when an enzyme that breaks RXA...Ch. 6 - Suppose that when an enzyme that breaks RXA chains...Ch. 6 - Devise an algorithm for generating all the...Ch. 6 - Devise an algorithm for generating all the...Ch. 6 - Prob. 57SECh. 6 - Prob. 58SECh. 6 - Prob. 1CPCh. 6 - Prob. 2CPCh. 6 - Prob. 3CPCh. 6 - Prob. 4CPCh. 6 - Given a positive integern,listallthe permutations...Ch. 6 - Prob. 6CPCh. 6 - Prob. 7CPCh. 6 - Prob. 8CPCh. 6 - Prob. 9CPCh. 6 - Prob. 10CPCh. 6 - Prob. 1CAECh. 6 - Prob. 2CAECh. 6 - Prob. 3CAECh. 6 - Prob. 4CAECh. 6 - Prob. 5CAECh. 6 - Prob. 6CAECh. 6 - Prob. 7CAECh. 6 - Prob. 8CAECh. 6 - Prob. 9CAECh. 6 - Describe some of the earliest uses of the...Ch. 6 - Prob. 2WPCh. 6 - Discuss the importance of combinatorial reasoning...Ch. 6 - Jlanv combinatonal identities are described in...Ch. 6 - Prob. 5WPCh. 6 - Prob. 6WPCh. 6 - Prob. 7WPCh. 6 - Describe the latest discoveries of values and...Ch. 6 - Prob. 9WPCh. 6 - Prob. 10WP

Additional Math Textbook Solutions

Find more solutions based on key concepts
Complete each statement with the correct term from the column on the right. Some of the choices may not be used...

Intermediate Algebra (13th Edition)

Let F be a continuous distribution function. If U is uniformly distributed on (0,1), find the distribution func...

A First Course in Probability (10th Edition)

1. How much money is Joe earning when he’s 30?

Pathways To Math Literacy (looseleaf)

For Problems 23-28, write in simpler form, as in Example 4. logbFG

Finite Mathematics for Business, Economics, Life Sciences and Social Sciences

Provide an example of a qualitative variable and an example of a quantitative variable.

Elementary Statistics ( 3rd International Edition ) Isbn:9781260092561

Testing Hypotheses. In Exercises 13-24, assume that a simple random sample has been selected and test the given...

Elementary Statistics Using The Ti-83/84 Plus Calculator, Books A La Carte Edition (5th Edition)

Knowledge Booster
Background pattern image
Math
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, subject and related others by exploring similar questions and additional content below.
Similar questions
Recommended textbooks for you
Text book image
Algebra: Structure And Method, Book 1
Algebra
ISBN:9780395977224
Author:Richard G. Brown, Mary P. Dolciani, Robert H. Sorgenfrey, William L. Cole
Publisher:McDougal Littell
Text book image
College Algebra (MindTap Course List)
Algebra
ISBN:9781305652231
Author:R. David Gustafson, Jeff Hughes
Publisher:Cengage Learning
Text book image
Intermediate Algebra
Algebra
ISBN:9781285195728
Author:Jerome E. Kaufmann, Karen L. Schwitters
Publisher:Cengage Learning
Text book image
Algebra for College Students
Algebra
ISBN:9781285195780
Author:Jerome E. Kaufmann, Karen L. Schwitters
Publisher:Cengage Learning
Text book image
College Algebra
Algebra
ISBN:9781938168383
Author:Jay Abramson
Publisher:OpenStax
Text book image
Holt Mcdougal Larson Pre-algebra: Student Edition...
Algebra
ISBN:9780547587776
Author:HOLT MCDOUGAL
Publisher:HOLT MCDOUGAL
SEE MORE TEXTBOOKS
Find number of persons in a part with 66 handshakes Combinations; Author: Anil Kumar;https://www.youtube.com/watch?v=33TgLi-wp3E;License: Standard YouTube License, CC-BY
Discrete Math 6.3.1 Permutations and Combinations; Author: Kimberly Brehm;https://www.youtube.com/watch?v=J1m9sB5XZQc;License: Standard YouTube License, CC-BY
How to use permutations and combinations; Author: Mario's Math Tutoring;https://www.youtube.com/watch?v=NEGxh_D7yKU;License: Standard YouTube License, CC-BY
Permutations and Combinations | Counting | Don't Memorise; Author: Don't Memorise;https://www.youtube.com/watch?v=0NAASclUm4k;License: Standard Youtube License
Permutations and Combinations Tutorial; Author: The Organic Chemistry Tutor;https://www.youtube.com/watch?v=XJnIdRXUi7A;License: Standard YouTube License, CC-BY