Concept & Short Tricks of Derangement in P&C

Duration: 11 min

This video lesson is available to enrolled students.

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Inside: a video lesson and guided study material.

Module outline

  1. About the Course: About the Course
  2. Paper-1 & 2 | Basic Numeracy: अनुपात और समानुपात / Ratio and Proportion, Divisibility Rules, मिश्रण और एलिगेशन / Mixture and Alligation, Permutation and Combination, Logarithm, संख्या पद्धति / Number System, महत्तम समापवर्तक और लघुत्तम समापवर्त्य / HCF and LCM, Sequence and Series (Series), समय, चाल और दूरी / Time, Speed and Distance, प्रतिशत / Percentage, औसत / Average, घन क्षेत्रमिति / Solid Mensuration, Age Problems, Arithmetic, Statistics, Probability, लाभ, हानि और बट्टा / Profit, Loss and Discount, साधारण और चक्रवृद्धि ब्याज / Simple and Compound Interest, Partnership, Speed Mathematics and Basic Mathematics, Algebra, सरलीकरण, घातांक और करणी / Simplification, Indices and Surds, समय और कार्य / Time and Work, Pipe and Cistern, RSSB Specific Videos - Basic Numeracy, समुच्चय, संबंध, फलन और विविक्त गणित / Sets, Relations, Functions and Discrete Mathematics, संख्या पद्धति और संख्या सिद्धांत / Number Systems and Number Theory, निर्देशांक ज्यामिति, सदिश और त्रिविमीय ज्यामिति / Coordinate Geometry, Vectors and 3D Geometry, बहुपद, समीकरण और सम्मिश्र संख्याएँ / Polynomials, Equations and Complex Numbers
  3. Paper-1 & 2 | Data Interpretation: आँकड़ा निर्वचन / Data Interpretation
  4. Paper-1 & 2 | General Mental Ability: Mental Ability, RSSB Specific Videos - Mental Ability
  5. Paper-1 & 2 | Logical Reasoning and Analytical Ability: श्रेणी / Series, कूट लेखन एवं कूट वाचन / Coding-Decoding, Data Sufficiency, अशाब्दिक तर्क / Non-Verbal Reasoning, Syllogisms, बैठक व्यवस्था एवं पहेलियाँ / Seating Arrangement and Puzzles, रक्त संबंध / Blood Relations, दिशा एवं दूरी / Direction and Distance, Analytical Reasoning (Counting Figures Reasoning), गणितीय संक्रियाएँ एवं लुप्त संख्या / Mathematical Operations and Missing Numbers, कैलेंडर एवं घड़ी / Calendar and Clock, Clock, घन, पासा एवं आकृतियों की गिनती / Cubes, Dice and Figure Counting, वेन आरेख, न्याय वाक्य एवं असमानता / Venn Diagrams, Syllogism and Inequalities, सादृश्यता एवं वर्गीकरण / Analogy and Classification, क्रम एवं रैंकिंग / Order and Ranking, कथन आधारित तार्किक विवेचन / Statement-Based Reasoning, Data Arrangement, वर्णमाला एवं संख्या परीक्षण / Alphabet and Number Test, Crypt Arithmetic
  6. Paper-1 & 2 | Decision Making and Problem Solving: आँकड़ों की पर्याप्तता एवं निर्णय क्षमता / Data Sufficiency and Decision Making
  7. Paper-1 | General Science: वैज्ञानिक उपलब्धियाँ और अनुसंधान / Scientific Achievements and Research, Biology, Chemistry, RSSB Specific Videos
  8. Paper-1 | General Awareness: राज्य विशेष सामान्य ज्ञान / State-Specific General Knowledge, समसामयिकी / Current Affairs
  9. Paper-2 | Fundamentals of Computer: Basics of COA, Number System, Floating Point Rep, Number Representation
  10. Paper - 2 | Digital Logic Systems: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits
  11. Paper-2 | Operating Systems: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling, File Management, Linux OS, Distributed Systems
  12. Paper-2 | Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, Relational Algebra, SQL, Relational Calculus, File Organization & Indexing, Transaction Management, Concurrency Control
  13. Paper-2 | Data Structures: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  14. Paper-2 | C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  15. Paper 2 | Oops, C++, Java: Language Design, OOPS with C++, Java, .Net Programming, Java Fundamentals
  16. Paper 2 | Python: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis
  17. Paper 2 | Emerging Trends and AI: Emerging Tech Trends, कंप्यूटर के मूल सिद्धांत / Computer Fundamentals, व्यापार, विपणन एवं उपभोक्ता संरक्षण / Trade, Marketing and Consumer Protection, कंप्यूटर नेटवर्क / Computer Networks
  18. Paper-2 | Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Advanced Algorithms
  19. Paper 2 | Data Communication and Network Security: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics, Network Security, Ethical Hacking
  20. Paper-2 I Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  21. Paper-2 | Computer Organization and Architecture: Cache Memory Organization, Input Output Organisation, Instr Formats & Modes, Control Unit Design, Register Transfer and Microoperations
  22. Paper-2 | Web Development: JavaScript-Basics, HTML Basics, CSS, XML
  23. Pedagogy: वृद्धि और विकास / Growth and Development, Concept of Pedagogy, संज्ञानात्मक प्रक्रियाएँ / Cognitive Processes, विकास के सिद्धांत / Theories of Development, समावेशी शिक्षा / Inclusive Education, Experiential Pedagogy, समाजीकरण और जेंडर / Socialisation and Gender, National Education Policy (NEP) 2020
  24. Live Sessions: RSSB Live Sessions
  25. RSSB Paper 1 - Full Mock Tests:
  26. RSSB Paper 2 - Full Mock Tests:
  27. SCI Previous Year Papers:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This educational video is a lecture on combinatorics, specifically focusing on permutations, combinations, and derangements. The instructor begins by introducing the concepts of permutation and combination using a visual metaphor of a locked box, clarifying that permutation is order-sensitive while combination is not. The main topic is derangements, which are permutations where no element appears in its original position. The video presents a problem involving 5 gems and 5 boxes, where no gem can be placed in its corresponding box. The instructor explains the formula for derangements, denoted as d_n, which is d_n = n! * Σ((-1)^k / k!) for k from 0 to n. He demonstrates the calculation for d_4 and d_5, using a table of values for n, d_n, and n! to find the final answer. The lecture uses a digital whiteboard for writing equations and diagrams, and includes a brief, humorous meme to illustrate a point about the problem's complexity.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with a title card that visually contrasts 'PERMUTATION' and 'COMBINATION' using a dice and a fruit basket. It then transitions to a slide titled 'Confused' which poses the question 'Should I unlock with Permutation or Combination?' and shows two locked boxes labeled 'Permutation' and 'Combination'. The instructor, Yash Jain, is visible in a small window, introducing the topic of permutations and combinations as part of a 'Basic To Advance' course. The slide also features a logo for 'Knowledge Gate Educator'.

  2. 2:00 – 5:00 02:00-05:00

    The instructor presents a problem on a digital whiteboard: 'There are 5 gems {g1,g2,g3,g4,g5} and 5 boxes {b1,b2,b3,b4,b5}. We are supposed to place exactly one gem in each box. Find number of ways to do so such that gem g(i) is not placed in box b(i) for all i={1,2,3,4,5}.' He explains that this is a classic problem of derangements, where no element is in its original position. He begins to write the formula for derangements, d_n = n! * Σ((-1)^k / k!) for k from 0 to n, and then starts to calculate d_4 as an example.

  3. 5:00 – 10:00 05:00-10:00

    The instructor continues the calculation for the derangement of 4 items, d_4. He writes out the formula: d_4 = 4! * [(-1)^0/0! + (-1)^1/1! + (-1)^2/2! + (-1)^3/3! + (-1)^4/4!]. He simplifies this to 24 * [1 - 1 + 1/2 - 1/6 + 1/24], which evaluates to 24 * [12/24 - 4/24 + 1/24] = 24 * [9/24] = 9. He then refers to a table of values for n, d_n, and n! to find that d_5 = 44. He concludes that the number of ways to place the 5 gems such that no gem is in its corresponding box is 44.

  4. 10:00 – 10:36 10:00-10:36

    The video concludes with a black screen displaying the text 'THANKS FOR WATCHING' in an orange and white box. The instructor's voice is heard saying 'Thank you for watching.' This is the final frame of the video, serving as an outro.

The video provides a clear and structured lesson on derangements, a key concept in combinatorics. It begins by establishing the foundational difference between permutations and combinations, using a relatable visual analogy. The core of the lecture is the application of the derangement formula to solve a specific problem. The instructor methodically breaks down the calculation, demonstrating the use of the formula for a smaller case (d_4) before applying it to the main problem (d_5). The use of a table of pre-calculated values for d_n and n! is a practical teaching aid. The overall progression is logical, moving from concept to formula to application, making the complex topic accessible to students.

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