Gopinath Munde
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A heap of wheat is in the form of a cone whose diameter is 10.5 m and height is 3 m. Find its volume. The heap is to be covered by canvas to protect it from rain. Find the area of the canvas required.

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NCERT Solutions for Class 9 Maths Chapter 13
Important NCERT Questions
Surface Areas and Volumes
NCERT Books for Session 2022-2023
CBSE Board, UP Board and Other state Boards
EXERCISE 13.7
Page No:233
Questions No:9

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2 Answers

  1. radius of heap of wheat r = 10.5/2 = 5.25 m and height h = 3 m
    Volume of heap of wheat = 1/3πr²h = 1/3 × 22/7 × 5.25 × 5.25 × 3 = 22 × 0.75 × 5.25 = 86.625 m³.
    Hence, the volume of heap of wheat is 86.625 m³.
    Let, the slant height of heap of wheat = l m
    We know that, l² = h² + r² ⇒ l² = 3² + (5.25)² ⇒ l² = 9 + 27.5625 ⇒ l² = 36.5625
    ⇒ l = √36.5625 = 6.05 m (approx.)
    Required area of canvas = πrl
    = 22/7 × 5.25 × 6.05 = 22 × 0.75 × 6.05 = 99.825 m²
    Hence, the required area of canvas to protect wheat is 99.825 m².

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  2. Get Hindi Medium and English Medium NCERT Solution for Class 9 Maths to download.
    Please follow the link to visit website for first and second term exams solutions.
    https://www.tiwariacademy.com/ncert-solutions/class-9/maths/chapter-13/

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