Ex 9.2, 16 - Chapter 9 Class 7 Perimeter and Area

Last updated at Dec. 16, 2024 by

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Ex 9.2, 16 How many times a wheel of radius 28 cm must rotate to go 352 m? (π‘‡π‘Žπ‘˜π‘’ πœ‹=22/7) In 1 rotation, wheel travels distance = Circumference Therefore, Number of rotations = (π‘«π’Šπ’”π’•π’‚π’π’„π’† 𝒕𝒓𝒂𝒗𝒆𝒍𝒍𝒆𝒅)/(π‘ͺπ’Šπ’“π’„π’–π’Žπ’‡π’†π’“π’†π’π’„π’† 𝒐𝒇 π’˜π’‰π’†π’†π’) Circumference of wheel Radius of wheel = r = 28 cm Circumference of wheel = 2πœ‹r = 2 Γ— 𝟐𝟐/πŸ• Γ— 28 = 2 Γ— 22 Γ— 4 = 44 Γ— 4 = 176 cm = 176 Γ— 1/100 m = 1.76 m Now Given, Distance travelled = 352 m Number of rotations = (π·π‘–π‘ π‘‘π‘Žπ‘›π‘π‘’ π‘‘π‘Ÿπ‘Žπ‘£π‘™π‘™π‘’π‘‘)/(πΆπ‘–π‘Ÿπ‘π‘’π‘šπ‘“π‘Ÿπ‘’π‘›π‘π‘’ π‘œπ‘“ π‘€β„Žπ‘’π‘’π‘™) ∴ Number of rotations = πŸ‘πŸ“πŸ/(𝟏.πŸ•πŸ”) = 352/176 Γ— 100 = πŸπŸ•πŸ”/πŸ–πŸ– Γ— 100 = 88/44 Γ— 100 = 2 Γ— 100 = 200 ∴ Wheel rotates 200 times

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Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo