NCERT Class 9 Maths | Chapter 11 Example 3 | Surface Areas & Volumes

In this video, we solve NCERT Class 9 Maths – Chapter 11: Surface Areas and Volumes, Example 3, where a real-life object (corn cob) is modeled as a cone to apply mensuration concepts. 👉 Radius of the broadest end of the corn cob = 2.1 cm 👉 Height (length) of the cob = 20 cm 👉 Each 1 cm² of the curved surface carries 4 grains of corn 👉 Using the curved surface area of a cone, we calculate the total number of grains on the cob This example is taken directly from NCERT; it shows how curved surface area is used in a practical situation. :contentReference[oaicite:0]{index=0} What you’ll learn: • How to treat everyday objects as geometric shapes • Finding slant height from radius and height • Applying the formula for curved surface area of a cone • Converting surface area to number-based results • Writing clean, step-by-step NCERT-style solutions for exams • Avoiding common student mistakes in board answers Key formulas used: • Slant height: l = √(r² + h²) – Derived from Pythagoras for a cone. :contentReference[oaicite:1]{index=1} • Curved surface area of a cone: π r l • Total grains = Curved Surface Area × grains per cm² Final answer: We compute the curved surface area, multiply by 4 grains per cm², and obtain the approximate total number of grains on the corn cob, matching NCERT’s result. :contentReference[oaicite:2]{index=2} Important for: CBSE Class 9 Maths | Chapter 11 | NCERT Examples | Board exam preparation App / extra resources: Download our Android App for more NCERT solutions and video lectures: 👉 https://play.google.com/... Engagement prompts: 👍 Like | 🔁 Share | 🔔 Subscribe for more exam-focused videos 📝 Comment your doubts or suggestions 📞 Call us: 999-266-1556 🌐 Visit: www.saraswatividyamandir.com SEO tags / Hashtags: #Class9Maths #SurfaceAreasAndVolumes #NCERTExample3 #Mensuration #ConeProblems #CBSE2025 #NCERTSolutions #Class9BoardExam #MathsConcepts #RealLifeMath