Volume Of Cylinder

Chapter 13 Class 9 Surface Areas and Volumes
Concept wise

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Ex 13.6, 2 The inner diameter of a cylindrical wooden pipe is 24 cm and its outer diameter is 28 cm. The length of the pipe is 35 cm. Find the mass of the pipe, if 1 cm3 of wood has a mass of 0.6 g. To find mass, we have to find volume of pipe Volume of pipe = Volume of outer cylinder β Volume of inner cylinder Outer cylinder Radius of outer cylinder = r1 = (π·πππππ‘ππ ππ ππ’π‘ππ ππ¦ππππππ)/2 = 28/2 = 14 cm Height of outer cylinder = h = 35 cm Volume of outer cylinder = ππ12β = π(14)2(35) Inner Cylinder Radius of inner cylinder = (π·πππππ‘ππ ππ πππππ ππ¦ππππππ)/2 = r2 = 24/2 = 12 cm Height of inner cylinder = h = 35 cm Volume of inner cylinder = ππ22β = π(12)2(35) Now, Volume of pipe = Volume of outer cylinder β Volume of inner Volume of pipe = π(14)2(35) β π(12)2(35) = π(35)( (14)2β(12)2) = 22/7Γ(35)Γ( 14 β12)(14+12) = 22 Γ 5 Γ 2 Γ 26 = 5720 cm3 Now it is given that Mass of 1 cm3 volume = 0.6 g β΄ Mass of 5720 cm3 volume = (5720 Γ 0.6) g = ((5720Γ0.6)/1000) kg = 3.432 kg. Therefore, mass of pipe is 3.432 kg