Demo: Tricks for HCF by Inspection, HCF by Prime Factorization

Duration: 18 min

This video lesson is available to enrolled students.

Return to /learn/UPESSC-ASSISTANT-TEACHER-RECRUITMENT/mathematics-practice/hcflcm-factors-divisibility-hcflcm/finding-hcf-lcm-1nqpxz1/asset-demo-tricks-for-hcf-by-inspection-hcf-by-prime-factorization after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. हिंदी / Hindi — भाषा खंड: भाषा, लिपि और वर्ण-विचार, संधि, शब्द-स्रोत और शब्द-रचना, समास, शब्द-भेद: विकारी और अविकारी, लिंग, वचन, कारक, काल और वाच्य, वाक्य-विचार और शुद्ध लेखन, शब्द-भंडार, रस, छंद, अलंकार और शब्द-शक्ति, अपठित बोध, हिंदी शिक्षणशास्त्र
  2. संस्कृत / Sanskrit — भाषा खंड: वर्णविचारः एवं संज्ञाप्रकरणम्, सन्धिप्रकरणम्, शब्दरूपाणि, धातुरूपाणि, कारकाणि एवं विभक्तयः, उपसर्गाः एवं अव्ययानि, प्रत्ययप्रकरणम्, समासप्रकरणम्, वाच्यप्रकरणम्, संख्याज्ञानम्, शब्दज्ञानम् एवं अनुवादः, अपठितावबोधनम्
  3. अंग्रेज़ी / English — भाषा खंड: Sounds, Spelling and Word Formation, Parts of Speech, Nouns and Pronouns, Articles, Determiners and Adjectives, Verbs and Modals, Tenses and Subject–Verb Agreement, Adverbs, Prepositions and Conjunctions, Sentence Structure, Voice and Narration, Vocabulary, Sentence Correction and Writing Skills, Poetry and English Literature, Reading Comprehension, Pedagogy of English Language
  4. सामान्य ज्ञान एवं समसामयिक घटनाएँ / General Knowledge & Current Affairs — 25 प्रश्न: भारतीय अर्थव्यवस्था: आँकड़े एवं समसामयिकी / Indian Economy: Data & Current Affairs, भारतीय कला एवं संस्कृति / Indian Art & Culture, विज्ञान एवं प्रौद्योगिकी / Science & Technology, पर्यावरण एवं जलवायु समसामयिकी / Environment & Climate Affairs, रक्षा एवं सुरक्षा / Defence & Security, स्थिर सामान्य ज्ञान / Static General Knowledge, पुरस्कार एवं सम्मान / Awards & Honours, खेल जगत / Sports, सरकारी योजनाएँ, शासन एवं आधारभूत संरचना / Government Schemes, Governance & Infrastructure, अंतरराष्ट्रीय संबंध एवं संगठन / International Relations & Organisations, प्रमुख नियुक्तियाँ एवं पदधारक / Key Appointments & Office Holders, उत्तर प्रदेश सामान्य ज्ञान / Uttar Pradesh GK
  5. गणित / Mathematics — 16 प्रश्न: संख्या पद्धति एवं स्थानीय मान / Number System & Place Value, मूलभूत संक्रियाएँ, सरलीकरण एवं पैटर्न / Basic Operations, Simplification & Patterns, गुणनखंड, विभाज्यता, म.स.प. एवं ल.स.प. / Factors, Divisibility, HCF & LCM, भिन्न एवं दशमलव / Fractions & Decimals, वर्ग, घन, घातांक एवं करणी / Squares, Cubes, Exponents & Surds, मापन: लंबाई, भार, धारिता, समय एवं मुद्रा / Measurement: Length, Mass, Capacity, Time & Money, बीजगणित / Algebra, अनुपात, समानुपात, औसत एवं आयु / Ratio, Proportion, Average & Ages, प्रतिशत, लाभ-हानि एवं ब्याज / Percentage, Profit–Loss & Interest, समय-कार्य एवं चाल-दूरी / Time & Work and Speed–Distance, रेखाएँ, कोण, आकृतियाँ एवं निर्देशांक / Lines, Angles, Shapes & Coordinates, त्रिभुज, चतुर्भुज, वृत्त एवं त्रिकोणमिति / Triangles, Quadrilaterals, Circles & Trigonometry, क्षेत्रमिति: परिमाप, क्षेत्रफल एवं आयतन / Mensuration: Perimeter, Area & Volume, आँकड़ा प्रबंधन, सांख्यिकी एवं प्रायिकता / Data Handling, Statistics & Probability, गणित शिक्षणशास्त्र / Mathematics Pedagogy
  6. विज्ञान / Science — 8 प्रश्न: प्रौद्योगिकी, मापन एवं गति / Technology, Measurement and Motion, बल, दाब, कार्य एवं ऊर्जा / Force, Pressure, Work and Energy, ऊष्मा एवं ध्वनि / Heat and Sound, प्रकाश / Light, विद्युत एवं चुंबकत्व / Electricity and Magnetism, ब्रह्मांड एवं प्राकृतिक परिघटनाएँ / Universe and Natural Phenomena, पदार्थ एवं उसकी संरचना / Matter and Its Structure, रासायनिक अभिक्रियाएँ, अम्ल, क्षार एवं लवण / Chemical Reactions, Acids, Bases and Salts, धातु, अधातु एवं दैनिक उपयोग की सामग्री / Metals, Non-metals and Materials of Daily Use, सजीव जगत: वर्गीकरण, कोशिका एवं ऊतक / Living World: Classification, Cell and Tissues, पादपों में पोषण, परिवहन एवं जनन / Plants: Nutrition, Transport and Reproduction, मानव शरीर एवं अंग तंत्र / Human Body and Organ Systems, भोजन, पोषण एवं स्वास्थ्य / Food, Nutrition and Health, पर्यावरण एवं पारिस्थितिकी / Environment and Ecology, विज्ञान शिक्षण शास्त्र / Science Pedagogy
  7. पर्यावरण एवं सामाजिक अध्ययन / Environment & Social Studies — 8 प्रश्न: प्राचीन भारत का इतिहास / Ancient Indian History, मध्यकालीन भारत का इतिहास / Medieval Indian History, औपनिवेशिक भारत एवं समाज सुधार / Colonial India and Social Reform, भारतीय राष्ट्रीय आंदोलन एवं स्वतंत्र भारत / Indian National Movement and Independent India, पृथ्वी, ग्लोब एवं मानचित्र / Earth, Globe and Maps, भौतिक भूगोल / Physical Geography, प्राकृतिक वनस्पति, वन्य जीवन एवं विश्व के प्रदेश / Natural Vegetation, Wildlife and World Regions, भारत का भूगोल / Geography of India, संसाधन एवं विकास / Resources and Development, सामाजिक एवं राजनीतिक जीवन / Social and Political Life, भारतीय संविधान / Indian Constitution, सरकार: केंद्र, राज्य एवं स्थानीय / Government: Union, State and Local, अर्थशास्त्र एवं भारतीय अर्थव्यवस्था / Economics and Indian Economy, सामाजिक विज्ञान शिक्षणशास्त्र / Social Science Pedagogy, परिवार, मित्र और समुदाय / Family, Friends and Community, पौधे / Plants, जंतु / Animals, खेती और पशुपालन / Farming and Animal Husbandry, भोजन और पोषण / Food and Nutrition, शरीर और स्वास्थ्य / Body and Health, जल / Water, आवास / Shelter, यात्रा, परिवहन और संचार / Travel, Transport and Communication, मानचित्र, दिशाएँ और भारत / Maps, Directions and India, हम क्या बनाते और करते हैं / Things We Make and Do, पृथ्वी, आकाश और आपदाएँ / Earth, Sky and Disasters, पर्यावरण, पारिस्थितिकी और वन्यजीव / Environment, Ecology and Wildlife, प्राकृतिक संसाधन, प्रदूषण और जलवायु परिवर्तन / Natural Resources, Pollution and Climate Change, पर्यावरण अध्ययन का शिक्षणशास्त्र / Pedagogy of Environmental Studies
  8. शिक्षण कौशल / Teaching Skills — 8 प्रश्न: पाठ्यचर्या और विद्यालयी गतिविधियाँ / Curriculum and School Activities, पाठ योजना और शिक्षण कौशल / Lesson Planning and Teaching Skills, शिक्षण संसाधन और शैक्षिक प्रौद्योगिकी / Teaching Resources and Educational Technology, कक्षा प्रबंधन और सम्प्रेषण / Classroom Management and Communication, विद्यालय नेतृत्व और प्रशासन / School Leadership and Administration, संविधान, आयोग, अधिनियम एवं योजनाएँ / Constitution, Commissions, Acts and Schemes in Education
  9. बाल मनोविज्ञान / Child Psychology — 8 प्रश्न: विकास की अवधारणा / Concept of Development, विकास के मनोवैज्ञानिक सिद्धांत / Psychological Theories of Development, व्यक्तिगत भिन्नताएँ, व्यक्तित्व एवं जेंडर / Individual Differences, Personality and Gender, बुद्धि एवं सृजनात्मकता / Intelligence and Creativity, अधिगम एवं इसके सिद्धांत / Learning and Its Theories, बालक कैसे सोचते एवं सीखते हैं / How Children Think and Learn, संवेग, अभिप्रेरणा, मानसिक स्वास्थ्य एवं निर्देशन / Emotion, Motivation, Mental Health and Guidance, समावेशी शिक्षा / Inclusive Education, शिक्षण-अधिगम प्रक्रिया / Teaching-Learning Process, शिक्षण विधियाँ एवं रणनीतियाँ / Teaching Methods and Strategies, आकलन एवं मूल्यांकन / Assessment and Evaluation, शैक्षिक विचारक, उद्देश्य एवं राष्ट्रीय नीतियाँ / Educational Thinkers, Aims and National Policies
  10. जीवन कौशल, प्रबन्धन एवं अभिवृत्ति / Life Skills, Management & Attitude — 8 प्रश्न: शिक्षक पहचान और व्यावसायिक विकास / Teacher Identity and Professional Development, जीवन कौशल, मूल्य, शांति एवं पर्यावरण शिक्षा / Life Skills, Values, Peace and Environmental Education
  11. तार्किक ज्ञान / Logical Reasoning — 5 प्रश्न: वर्णमाला एवं संख्या परीक्षण / Alphabet & Number Test, श्रृंखला / Series, सादृश्यता एवं वर्गीकरण / Analogy & Classification, कूटलेखन एवं कूटवाचन / Coding-Decoding, गणितीय संक्रियाएँ एवं अंकगणितीय तर्क / Mathematical Operations & Arithmetical Reasoning, रक्त संबंध / Blood Relations, दिशा एवं दूरी / Direction & Distance, क्रम, बैठक व्यवस्था एवं पहेली / Ranking, Seating Arrangement & Puzzles, कैलेंडर एवं घड़ी / Calendar & Clock, वेन आरेख एवं तार्किक निगमन / Venn Diagrams & Logical Deduction, कथन आधारित तर्क / Statement-Based Reasoning, अशाब्दिक तर्क / Non-Verbal Reasoning, पासा एवं घन / Dice & Cubes
  12. सूचना तकनीकी / Information Technology — 4 प्रश्न: कंप्यूटर का परिचय / Introduction to Computers, कंप्यूटर हार्डवेयर एवं परिधीय उपकरण / Computer Hardware and Peripherals, कंप्यूटर मेमोरी / Computer Memory, संख्या पद्धति एवं डेटा निरूपण / Number System and Data Representation, सॉफ्टवेयर एवं प्रोग्रामिंग भाषाएँ / Software and Programming Languages, ऑपरेटिंग सिस्टम / Operating System, एमएस ऑफिस / MS Office, डेटाबेस प्रबंधन प्रणाली (DBMS) / Database Management System (DBMS), कंप्यूटर नेटवर्क / Computer Networks, इंटरनेट एवं उसकी सेवाएँ / Internet and its Services, साइबर सुरक्षा / Cyber Security, डिजिटल समाज, आईटी अधिनियम एवं ई-गवर्नेंस / Digital Society, IT Act and E-Governance, उभरती तकनीकें / Emerging Technologies, शिक्षा में ICT / ICT in Education
  13. अतिरिक्त अभ्यास (वैकल्पिक) / Extra Practice — beyond the 2026 syllabus: विश्व इतिहास एवं अंतरराष्ट्रीय संबंध / World History and International Relations, संस्कृतसाहित्यम् एवं काव्यशास्त्रम्, संस्कृतशिक्षणशास्त्रम्, हिंदी साहित्य
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This educational video provides a comprehensive tutorial on calculating the Highest Common Factor (HCF), also known as the Greatest Common Divisor (GCD). The instructor begins by establishing foundational definitions, explaining that a factor is a number that divides another number exactly without leaving a remainder. Using the number 12 as an illustrative example, the instructor lists all integers from 1 to 12 and demonstrates which ones divide evenly (1, 2, 3, 4, 6, 12) versus those that do not (like 7). The lesson then progresses to defining HCF as the largest number common to two or more sets of factors. Two primary methods for finding the HCF are introduced and demonstrated: inspection and prime factorization. The inspection method involves listing all factors of the given numbers and identifying the largest shared value, which is noted to be effective only for small integers. The prime factorization method involves breaking numbers down into their constituent prime factors and multiplying the common primes to find the HCF. The video concludes by highlighting the limitations of these manual methods when applied to large numbers with complex exponents, suggesting alternative tools for such cases.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with an introduction to the concepts of Highest Common Factor (HCF) and Least Common Multiple (LCM). The instructor immediately demonstrates the division method for finding HCF using specific numerical examples on a digital chalkboard. Visual aids include step-by-step calculations showing the division process for both HCF and LCM problems, such as finding the HCF of 455 and 26. The instructor writes 'HCF And LCM' as the title and proceeds to solve a problem involving 6, 96, and 12. Key on-screen text includes 'Highest Common Factor (HCF)' and division notations like '26)455(17'. The instructor underlines key terms and uses a grid layout to organize multi-number division, ensuring students visualize the long division process clearly.

  2. 2:00 – 5:00 02:00-05:00

    The instructor shifts focus to defining factors (divisors) by writing the question 'What is Factor (Divisor)?' on the screen. He illustrates this concept using the number 12, writing its multiplication form as '3 x 4' and establishing a range from 1 to 12. The instructor lists all numbers in this range and checks divisibility with checkmarks or crosses, demonstrating that dividing 12 by factors like 3 results in whole numbers (4), while non-factors do not. The text '12 = {1, 2, 3, 4, 6, 12}' appears to summarize the factors. The instructor then introduces finding the HCF of 6 and 8 by listing their respective factors: 'Factors of 6 = {1, 2, 3, 6}' and 'Factors of 8 = {1, 2, 4, 8}'. He begins to write the word 'Common' to identify shared factors between these sets.

  3. 5:00 – 10:00 05:00-10:00

    This segment demonstrates finding the HCF using the inspection method. The instructor lists all factors for two numbers, 12 and 18, to identify their common divisors. The text 'HCF by Inspection' is displayed alongside the problem 'HCF (12, 18)'. The factors are listed as 'Factors(12) = {1, 2, 3, 4, 6, 12}' and 'Factors(18) = {1, 2, 3, 6, 9, 18}'. By comparing these sets, the instructor identifies 'CF(12, 18) = {1, 2, 3, 6}' and selects the highest value, 'HCF(12, 18) = {6}'. The video then introduces the second method, HCF by Prime Factorization. A note appears stating 'HCF by Inspection - This method can be used only for small numbers'. The instructor transitions to an example problem 'HCF (24, 40)' and begins demonstrating the division ladder method to break down these numbers into prime factors.

  4. 10:00 – 15:00 10:00-15:00

    The instructor demonstrates finding the HCF using prime factorization for two different sets of numbers. First, he solves 'HCF(24, 40)' by breaking down both numbers into prime factors: '24 = 2 x 2 x 2 x 3' and '40 = 2 x 2 x 2 x 5'. He identifies the common factors as '2x2x2=8'. The method is then applied to a new problem, 'HCF(12, 30, 48)'. The prime factorizations are written as '12 = 2 x 2 x 3', '30 = 2 x 3 x 5', and '48 = 2 x 2 x 2 x 2 x 3'. The instructor highlights the common prime factors across all three numbers to determine the final HCF, calculated as '2^1 x 3^1 = 6'. A note appears stating this method is best for small numbers where prime factors are easily found.

  5. 15:00 – 17:55 15:00-17:55

    The video transitions from the detailed example of finding the HCF for small numbers (12, 30, 48) to a more complex problem involving large numbers with exponents. The instructor highlights that the prime factorization method is practical only for small numbers where factors are easily identifiable. He presents a problem with three large composite numbers expressed in prime factor form: '1. Find the H.C.F. of 2^3 x 3^2 x 5 x 7^4 x 13^4, 2^2 x 3^5 x 5^2 x 7^8, 2^3 x 5^3 x 7^2 x 13^3'. The instructor indicates that manual calculation is difficult for such large values, suggesting the use of a calculator or alternative methods. Visual cues include crossing out non-common factors and emphasizing the limitation that 'Method can only be used for small numbers and numbers whose prime factors can be found easily'.

The lecture systematically builds the concept of HCF from basic definitions to advanced application. It begins by defining factors as divisors that result in whole numbers, using 12 to illustrate the concept visually. The instructor then defines HCF as the greatest shared factor between numbers, demonstrating this through listing factors for 6 and 8. Two distinct methods are taught: inspection, which is limited to small numbers due to the manual listing required, and prime factorization, which involves decomposing numbers into primes. The video emphasizes that while inspection is intuitive for small integers like 12 and 18, prime factorization offers a structured approach but remains practical only for numbers with easily identifiable factors. The final segment warns against applying these manual methods to large composite numbers with high exponents, such as those involving 7^4 or 13^8, where calculation becomes unwieldy. This progression ensures students understand both the mechanics of finding HCF and the practical constraints of each method.

Loading lesson…