Quick Revision & Practice Problem

Duration: 1 hr 2 min

This video lesson is available to enrolled students.

Return to /learn/BIHAR-STET-COMPUTER-SCIENCE-COMPLETE-COURSE/mathematical-aptitude/divisibility-rules/multiple-topics/asset-quick-revision-practice-problem after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. About the course: About the Course
  2. Mathematical Aptitude: संख्या पद्धति / Number System, महत्तम समापवर्तक और लघुत्तम समापवर्त्य / HCF and LCM, Divisibility Rules, प्रतिशत / Percentage, अनुपात और समानुपात / Ratio and Proportion, औसत / Average, लाभ, हानि और बट्टा / Profit, Loss and Discount, समय और कार्य / Time and Work, घन क्षेत्रमिति / Solid Mensuration, साधारण और चक्रवृद्धि ब्याज / Simple and Compound Interest, समय, चाल और दूरी / Time, Speed and Distance, Age Problems, मिश्रण और एलिगेशन / Mixture and Alligation, Algebra, सरलीकरण, घातांक और करणी / Simplification, Indices and Surds, Pipe and Cistern, Trigonometry, Statistics, आँकड़ा निर्वचन / Data Interpretation, Arithmetic, 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. Logical Reasoning: श्रेणी / Series, कूट लेखन एवं कूट वाचन / Coding-Decoding, सादृश्यता एवं वर्गीकरण / Analogy and Classification, रक्त संबंध / Blood Relations, दिशा एवं दूरी / Direction and Distance, क्रम एवं रैंकिंग / Order and Ranking, अशाब्दिक तर्क / Non-Verbal Reasoning, बैठक व्यवस्था एवं पहेलियाँ / Seating Arrangement and Puzzles, Syllogisms, वेन आरेख, न्याय वाक्य एवं असमानता / Venn Diagrams, Syllogism and Inequalities, गणितीय संक्रियाएँ एवं लुप्त संख्या / Mathematical Operations and Missing Numbers, वर्णमाला एवं संख्या परीक्षण / Alphabet and Number Test, कथन आधारित तार्किक विवेचन / Statement-Based Reasoning, Analytical Reasoning (Counting Figures Reasoning), घन, पासा एवं आकृतियों की गिनती / Cubes, Dice and Figure Counting, कैलेंडर एवं घड़ी / Calendar and Clock, Clock
  4. General Knowledge: वैज्ञानिक उपलब्धियाँ और अनुसंधान / Scientific Achievements and Research, Chemistry, Biology, History, Geography, Polity, Indian Economy, समसामयिकी / Current Affairs, Static General Knowledge
  5. Art of Teaching: शिक्षण-अधिगम प्रक्रिया एवं कक्षा प्रबंधन / Teaching-Learning Process and Classroom Management, Learners & Learning Process, Factors Affecting Teaching, शिक्षण विधियाँ एवं उपागम / Teaching Methods and Approaches, सूक्ष्म शिक्षण एवं कक्षा संप्रेषण / Microteaching and Classroom Communication, शिक्षण सहायक सामग्री एवं शैक्षिक तकनीकी / Teaching Aids and Educational Technology, आकलन एवं मूल्यांकन / Assessment and Evaluation, शिक्षक: गुण, व्यावसायिक नैतिकता एवं विकास / Teacher: Qualities, Professional Ethics and Development, शैक्षिक नीतियाँ, अधिनियम एवं प्रशासन / Educational Policies, Acts and Administration, पाठ्यचर्या, कला एवं सह-शैक्षिक क्षेत्र / Curriculum, Arts and Co-curricular Areas, निर्देशन एवं परामर्श / Guidance and Counselling, दिव्यांग बच्चों की शिक्षा / Education of Children with Disabilities, Micro-Teaching & Teaching Skills, पाठ योजना / Lesson Planning
  6. Environmental Science: Environment
  7. Unit 1 | Digital Electronics: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation
  8. Unit 2 | COA: Basics of COA, Floating Point Rep, Cache Memory Organization, Input Output Organisation, Instr Formats & Modes, Control Unit Design, Register Transfer and Microoperations, Programming the Basic Computer
  9. Unit 3 | C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  10. Unit 3 | Data Structures: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  11. Unit 4 | Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  12. Unit 5 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management
  13. Unit 6 | Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Transaction Management, Concurrency Control
  14. Unit 7 | Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer
  15. Unit 8 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  16. Unit 9 | Object Oriented Programming: OOPS with C++
  17. Unit 10 | Web Development: HTML Basics, CSS, JavaScript-Basics, XML, Node.js
  18. Unit 11 | Theory Of Computation: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines
  19. Unit 12 | IoT: Emerging Tech Trends, Cloud Computing, कंप्यूटर नेटवर्क / Computer Networks
  20. Unit 13 | Artificial Intelligence: Approaches to AI, Search Algorithms, Game Playing, Knowledge Representation, Natural Language Processing, Artificial Neural Networks, Genetic Algorithms
  21. Unit 14 | E-Commerce: Electronic Data Interchange and E-Commerce, Role of Internet and Web Services, Security in Mobile and Wireless Computing, Physical Security and Cryptography Basics, Cyber Safety and Security
  22. Unit 15 | Multimedia: Multimedia
  23. Unit 16 | Python: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis, DSA using Python
  24. Full Length Mock Tests — General Paper:
  25. Full Length Mock Tests — Computer Science (Paper II):
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture provides a structured revision of divisibility rules, progressing from basic single-digit tests to composite numbers and larger primes, before applying these concepts to quantitative aptitude practice problems. The session begins by defining divisibility and introducing rules for 2, 3, 4, and 5. The instructor uses a whiteboard to demonstrate factor sets for the number 12, showing how multiples of 12 are formed by dividing 24 by its factors. The lesson then covers the rule for 6 (passing both 2 and 3 tests) and a place-value breakdown method for dividing 672 by 7. Further rules are introduced for 9, 10, and the alternating sum rule for 11. The instructor transitions to composite rules for 12 (passing both 3 and 4) and introduces specialized tests for primes like 13, 16, and 17. A memorization table is presented for primes from 11 to 43, using specific factors (e.g., -5 for 17, +2 for 19) to simplify calculations. The final segment focuses on practice problems, including finding missing digits 'K' in numbers divisible by 11 and determining the maximum number of 4-digit permutations from a given set that are divisible by 9.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The lecture opens with a slide titled "Divisibility Rules," defining the concept as testing if one number can be exactly divided by another. Examples include "14 is divisible by 7" and "0 is divisible by 7." The instructor then works through the rule for 3 using the example "Is 723 divisible by 3?" showing that 7+2+3=12, which is divisible by 3. The rule for 2 is also introduced, noting that the last digit must be even (0, 2, 4, 6, 8), with examples like 128 (Yes) and 129 (No).

  2. 2:00 – 5:00 02:00-05:00

    The instructor continues with the rule for 3, using examples like 381 (sum is 12) and 217 (sum is 10). The rule for 4 is introduced, stating that the last two digits must be divisible by 4. Examples include 1312 (Yes) and 7019 (No). A quick check for small numbers is provided: halving the number twice. The lesson transitions to rule 5, where the last digit must be 0 or 5. On the whiteboard, the instructor writes the fraction 24/12 and lists the factors of 12 as {1, 2, 3, 4, 6, 12}.

  3. 5:00 – 10:00 05:00-10:00

    The whiteboard shows a circled "24" and the set of factors for 12, with fractions like 24/1 through 24/12 each followed by a check mark. A slide for rule 6 states that a number must be even and divisible by 3. Examples include 14 (Yes) and 808 (No). The instructor then demonstrates a place-value breakdown for dividing 672 by 7, showing intermediate steps like subtracting 4 from 67 to get a remainder of 63, and eventually reaching a final remainder of 0.

  4. 10:00 – 15:00 10:00-15:00

    The video covers rules for 9, 10, and 11. For 9, the sum of digits must be divisible by 9 (e.g., 1629). For 10, the number must end in 0 (e.g., 220). For 11, the instructor explains the alternating sum rule: adding and subtracting digits in an alternating pattern. A detailed example for 1364 is shown, where +1-3+6-4 = 0, confirming divisibility. The instructor also works through the example of 987, where +9-8+7 = 8 (No).

  5. 15:00 – 20:00 15:00-20:00

    The instructor reviews the rule for 11 with examples like 286 and 14641, where +1-4+6-4+1 = 0. A long division of 1464 by 11 is performed to verify the result. The lesson then transitions to composite numbers, explaining that a number is divisible by 12 if it passes both the 3 and 4 rules. Examples include 648 (Yes) and 524 (No). The rule for 13 is introduced: adding four times the last digit to the remaining truncated number, using 50661 as an example.

  6. 20:00 – 25:00 20:00-25:00

    The rule for 16 is presented, stating that the last four digits must be divisible by 16. An example given is 157,648, where 7,648 = 478 × 16. An alternative method for 16 is shown: adding the last two digits to four times the rest. The rule for 17 follows, which involves subtracting five times the last digit from the remaining leading truncated number. An example is 3978, which becomes 397 - (5*8) = 357.

  7. 25:00 – 30:00 25:00-30:00

    The instructor continues with the rule for 16, noting that if the thousands digit is even, the last three digits must be divisible by 16 (e.g., 254,176). The rule for 17 is demonstrated again with the example 221, where 22 - (1*5) = 17. The instructor uses underlining and circling on the board to highlight key terms and specific digits in these calculations, emphasizing the iterative nature of these tests for larger primes.

  8. 30:00 – 35:00 30:00-35:00

    A table is displayed listing divisibility factors for primes from 11 to 43. The instructor writes numbers like 145, 273, and 311 on the whiteboard with associated keywords like 'Recharge' and 'Lipstick' to aid memorization. The table shows specific factors such as -1 for 11, +4 for 13, and -5 for 17. The instructor explains how to group these numbers based on their positive or negative factors to simplify the application of the rules.

  9. 35:00 – 40:00 35:00-40:00

    The instructor points to the table of factors for primes 11-43, explaining how to use them. A slide details the test for divisibility by 41: subtract four times the last digit from the remaining number. A step-by-step calculation for 30873 is shown: 307 - (4*3) = 295, then 29 - (4*5) = 9, and finally reaching a remainder of zero. This demonstrates the iterative process until a recognizable number or zero is reached.

  10. 40:00 – 45:00 40:00-45:00

    The video shows a quick revision of rules for 7 and 11. A practice problem is introduced: "2ab5 is a four-digit number divisible by 25." The instructor identifies that for divisibility by 25, the last two digits must be 00, 25, 50, or 75. The problem states that the digits 'ab' form a multiple of 13. Options A (65), B (75), C (52), and D (25) are evaluated. The instructor identifies 52 as the correct answer because it is a multiple of 13 and fits the constraints.

  11. 45:00 – 50:00 45:00-50:00

    A new problem is introduced asking for the smallest whole number 'K' to make 97215k6 divisible by 11. The instructor sets up the alternating sum equation: +9 -7 +2 -1 +5 -k = 0/11n. Solving this equation leads to K=3, which matches option B on the screen. The instructor emphasizes using the alternating sum rule to find missing digits in quantitative aptitude problems.

  12. 50:00 – 55:00 50:00-55:00

    The instructor solves another problem for a missing digit 'K' in the number K35624, which is divisible by 11. The equation +K -3 +5 -6 +2 -4 = 0/11n is set up and simplified to K-6=0. The instructor concludes that K=6 is the valid single-digit solution, explicitly rejecting K=17 because it does not fit the constraint of being a single digit. This reinforces the importance of checking solution validity.

  13. 55:00 – 60:00 55:00-60:00

    A series of quantitative aptitude problems is presented. The first asks for the maximum number of 4-digit numbers formed by digits 6, 4, 8, and 1 that are divisible by 9. The instructor calculates the sum of these digits as 19 (6+4+8+1=19), which is not divisible by 9, leading to an answer of 0. A subsequent problem asks for the largest 5-digit number exactly divisible by 93, with option B (99,624) being pointed out.

  14. 60:00 – 61:31 60:00-61:31

    The lecture concludes with a final review of the practice problems. The instructor reiterates that for any number formed from a fixed set of digits, the sum of those digits must be divisible by 9 for any permutation to be valid. The session ends with a summary of the key divisibility rules covered, from basic single-digit tests to the specialized factors for primes up to 43.

The lecture follows a logical progression from foundational divisibility rules to complex applications. It starts with the basics (2, 3, 4, 5) and moves to composite rules (6, 12), where a number must satisfy multiple conditions. The instructor then introduces the alternating sum rule for 11 and specialized truncation rules for larger primes (13, 16, 17). A key pedagogical tool is the use of a factor table for primes up to 43, which allows students to apply a consistent 'add or subtract factor times last digit' method. The final portion of the video applies these rules to solve for missing digits in numbers, a common format in quantitative aptitude exams. The instructor emphasizes the importance of checking if solutions are valid single digits and using digit sums to quickly eliminate impossible permutations.

Loading lesson…