3D Geometry Important Question

Duration: 5 min

This video lesson is available to enrolled students.

Return to /learn/CTET-PAPER-1/mathematics-legacy/mensuration-and-geometry/3d-mensuration-solid-figures/asset-3d-geometry-important-question after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. Child Development and Pedagogy: Concept of Pedagogy, Psychology, Child Development, Theories, Personality Development, Individual Differences, Learning and Motivation, Understanding Diverse Learners, Inclusive Education, Mental Health & Life Skills, Teaching-Learning Process, Teaching Methods & Strategies, Experiential Pedagogy, Assessment & Evaluation, National Education Policy (NEP) 2020, Curriculum Framework & Reforms, Miscellaneous Topics, Learners & Learning Process, Factors Affecting Teaching, Methods of Teaching, Classroom Management & Communication, Teaching-Learning Aids & ICT Integration, Curriculum & School Environment, Evaluation, Assessment & Measurement, Inclusive Education & Special Needs
  2. Mathematics: Number System & Place Value, Whole Numbers & Four Operations, Factors, Multiples, Divisibility, HCF & LCM, Fractions & Decimals, Patterns, Ratio, Proportion & Percentage, Measurement — Length, Mass, Capacity, Time, Money, Geometry — Shapes, Lines & Angles, Symmetry, Spatial Understanding, Mensuration — Perimeter, Area, Surface Area, Volume, Data Handling, Graphs & Probability, Mathematics Pedagogy
  3. Environmental Studies: Family & Friends, Relationships, Community, Food & Nutrition, Health & Hygiene, Shelter & Houses, Water (sources, conservation), Travel, Transport & Communication, Things We Make & Do (materials, occupations, crafts), Plants (types, parts, uses), Animals (habitats, features, care), Our Body & Senses, Air, Weather, Sky & Seasons, Maps, Directions & Local Environment, Festivals, Culture & Heritage (India), Environment Conservation, Waste & Pollution, Natural Disasters & Safety, EVS Pedagogy
  4. Language I/II — Hindi: वर्ण-विचार (भाषा, लिपि और वर्णमाला), वर्तनी और वर्ण-विन्यास, शब्द, पद और शब्द-भेद, संज्ञा और सर्वनाम, विशेषण और क्रिया, लिंग, वचन, पुरुष और कारक, काल, वाच्य, वाक्य और वाक्य-भेद, संधि, समास, विलोम शब्द, शब्द-भंडार, सामान्य अशुद्धियाँ (Samanya Ashuddhiyaan), अनेक शब्दों के लिए एक शब्द, मुहावरे और लोकोक्तियाँ, अपठित गद्यांश और अपठित पद्यांश, Multi-Topic Content (Cross-Concept Material), वर्णमाला (Varnmala), वाक्य-शुद्धि, अशुद्धि शोधन और विराम चिह्न, उपसर्ग और प्रत्यय, तत्सम, तद्भव, देशज और विदेशी शब्द, अनेकार्थी और शब्द-युग्म, अलंकार, रस और छंद, शब्दोत्पत्ति एवं भाषा-बोलियाँ, वाक्य-पूर्ति और अनुच्छेद-रचना
  5. Language I/II — English: Noun, Pronoun, Determiner, Articles, Adjectives, Verb, Adverb, Preposition, Conjunction, Interjection, Sentence Structure, Phrases & Clauses, Tenses, Subject Verb Agreement (Verb Noun Agreement), Modals, Active Passive Voice (Voice), Direct and Indirect Speech, Vocabulary, Sentence Construction, Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Cloze Test (Cloze Passage), Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing)
  6. Language I/II — Sanskrit: वर्ण, उच्चारण, सन्धि, शब्दरूप, धातुरूप, कारक-विभक्ति, समास, प्रत्यय, उपसर्ग, वाच्य, सङ्ख्या, अव्यय, अपठित अवबोधन
  7. Language I/II — Urdu: Spelling & Diacritics, Vocabulary, Grammar (اسم, فعل, صفت, ضمیر), Idioms & Proverbs, Comprehension
  8. Language I/II — Bengali: Grammar, Vocabulary, Idioms & Expressions, Writing & Composition, Comprehension
  9. Language Pedagogy (Language I and II): Language Pedagogy (Hindi/English/Sanskrit/Urdu learning & teaching)
  10. Mathematics (Video Lessons & Notes): Number System, Arithmetic, Divisibility Rules, HCF LCM, Speed Mathematics and Basic Mathematics, Mensuration and Geometry, Statistics, Mental Ability
  11. Environmental Studies (Video Lessons & Notes): Environment, Ecosystem, Biomes & Environmental Issues, Air Pollution, Water Pollution, Soil, Noise Pollution and Waste Management, Natural Resources, Energy & Disaster Management, Global Environmental Conventions – COP, Protocols & ISA, MDG & SDG
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This bilingual 3D geometry lesson solves a right-prism problem: the triangular base has sides 20 cm, 21 cm and 29 cm; volume is 7560 cm³; find lateral surface area. The instructor first computes the base perimeter P = 20 + 21 + 29 = 70 cm. A red right-triangle is sketched on the prism’s end face, and the Pythagorean check 20² + 21² = 29² (400 + 441 = 841) confirms the base is a right triangle, so its area is ½ × b × h = ½ × 20 × 21 = 210 cm². Using volume V = base area × prism height, the instructor finds h = 7560 / 210 = 36 cm. Finally, lateral surface area LSA = P × h = 70 × 36 = 2520 cm², matching option 4. The method emphasizes recognizing a right-triangle base from side lengths, computing area via ½bh, extracting prism height from volume, and applying LSA = perimeter × height.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The bilingual problem is displayed in English and Hindi: a right-prism with triangular base sides 20 cm, 21 cm, 29 cm and volume 7560 cm³; options are 2448, 2556, 2484, 2520 cm². A light-blue wireframe triangular prism appears at lower left. The instructor begins red handwritten work: perimeter P = 20 + 21 + 29 = 70 cm, then boxes the triangle area formula ½ × b × h and sketches a red right-triangle on the prism’s end face to mark base and height.

  2. 2:00 – 4:39 02:00-04:39

    The instructor verifies the base is a right triangle by writing 20² + 21² = 29² and 400 + 441 = 841, then computes base area as ½ × 20 × 21 = 210 cm². Using volume, the prism height is found: h = 7560 / 210 = 36 cm. The lateral surface area is then calculated with LSA = P × h = 70 × 36 = 2520 cm², and the answer is circled as option 4.

The lesson teaches a systematic approach to right-prism lateral surface area when the base is a triangle. Key steps: (1) compute perimeter from side lengths; (2) test for a right triangle using the Pythagorean theorem to justify area = ½bh; (3) compute base area; (4) derive prism height from V = base area × h; (5) apply LSA = perimeter × height. The worked example yields 2520 cm², reinforcing that lateral surface area depends only on base perimeter and prism height, not on the shape’s internal angles once area is known.

Loading lesson…