Short Tricks to Find Unit Digit of an Expression (2)

Duration: 19 min

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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 finding the unit digit of large exponential numbers, a common problem in competitive exams. The instructor begins by introducing the concept of unit digit cyclicity, explaining that the unit digit of a number raised to a power follows a repeating pattern. The lesson systematically breaks down the behavior of digits 0 through 9. It first establishes that digits 0, 1, 5, and 6 have a cyclicity of 1, meaning their unit digit remains unchanged regardless of the power. Next, it covers digits 4 and 9, which have a cyclicity of 2, with their unit digits alternating between two values based on whether the exponent is odd or even. The core of the lesson focuses on digits 2, 3, 7, and 8, which all have a cyclicity of 4, meaning their unit digits cycle through four different values. The instructor demonstrates this by calculating the first few powers of each digit (e.g., 2^1=2, 2^2=4, 2^3=8, 2^4=16) to identify the repeating cycle. The video concludes by presenting a summary table that consolidates the cyclicity and power cycles for all digits 0-9, providing a quick reference for students. The entire explanation is supported by on-screen text, handwritten calculations, and a clear, step-by-step teaching approach.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with a title slide for a lesson on the 'NUMBER SYSTEM' by Yash Jain of Knowledge Gate Eduventures. The instructor introduces the topic, which is to find the unit digit of large exponential numbers. The first concept presented is that digits 0, 1, 5, and 6 have a cyclicity of 1, meaning their unit digit remains the same when raised to any power. For example, the text on screen states: '0^n = 0, 1^n = 1, 5^n = 5, 6^n = 6.' This establishes the foundation for the lesson.

  2. 2:00 – 5:00 02:00-05:00

    The instructor explains the cyclicity of digits 4 and 9, which have a cycle of 2. The on-screen text states: 'Digits 4 & 9: Both these numbers have a cyclicity of only two different digits as their unit digit.' The instructor demonstrates this by calculating the powers of 4: 4^1 = 4 (unit digit 4), 4^2 = 16 (unit digit 6), 4^3 = 64 (unit digit 4), and 4^4 = 256 (unit digit 6). This shows a repeating pattern of 4 and 6. The same logic is applied to 9, where 9^1 = 9, 9^2 = 81, 9^3 = 729, etc., showing a cycle of 9 and 1. The key takeaway is that for these digits, the unit digit depends on whether the exponent is odd or even.

  3. 5:00 – 10:00 05:00-10:00

    The lesson progresses to the most complex case: digits 2, 3, 7, and 8, which have a cyclicity of 4. The on-screen text states: 'Digits 2, 3, 7 & 8: These numbers have a power cycle of 4 different numbers.' The instructor demonstrates this by showing the power cycles. For digit 2: 2^1 = 2, 2^2 = 4, 2^3 = 8, 2^4 = 16, and then the cycle repeats (2, 4, 8, 6). For digit 3: 3^1 = 3, 3^2 = 9, 3^3 = 27, 3^4 = 81, and then the cycle repeats (3, 9, 7, 1). The same pattern is shown for 7 and 8. The method to solve a problem is to find the remainder when the exponent is divided by 4, which determines the position in the 4-step cycle.

  4. 10:00 – 15:00 10:00-15:00

    The instructor applies the learned concepts to solve a specific problem: finding the unit digit of 287^562581. The on-screen text shows the problem statement. The solution involves identifying the unit digit of the base, which is 7. The instructor then refers to the previously established rule that the unit digit of 7 follows a cycle of 4: 7, 9, 3, 1. To find the unit digit of 7^562581, the exponent 562581 is divided by 4. The remainder is 1 (since 562581 = 4*140645 + 1). This means the unit digit corresponds to the first number in the cycle, which is 7. The instructor also shows a list of other problems for practice, such as 185^563 and 271^6987, to reinforce the method.

  5. 15:00 – 18:33 15:00-18:33

    The video concludes with a summary table that consolidates all the concepts. The table, titled 'Cyclicity Table', lists the digits 0-9, their cyclicity (1, 2, or 4), and their power cycle. For example, it shows that digit 2 has a cyclicity of 4 and a power cycle of 2, 4, 8, 6. The instructor reviews the table, circling the key values. The final frame is a 'Thank You for Watching' message, indicating the end of the lesson.

The video presents a structured and logical progression for solving unit digit problems. It begins with the simplest cases (digits with cyclicity 1) and builds complexity by introducing digits with cyclicity 2 and then the most common case (cyclicity 4). The core method is to identify the unit digit of the base, determine its cyclicity, and then use the remainder of the exponent divided by the cyclicity to find the corresponding digit in the cycle. This systematic approach, reinforced by a summary table, provides students with a reliable and efficient strategy for tackling these types of questions in exams.

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