Ex 13.2, 3 - A metal pipe is 77 cm long. The inner diameter - Area Of Cylinder

  1. Class 9
  2. Important Questions for Exam - Class 9

Transcript

Ex 13.2, 3 A metal pipe is 77 cm long. The inner diameter of a cross section is 4 cm, the outer diameter being 4.4 cm. Inner curved surface area, Inner radius of cylindrical pipe = r1 = ( )/2 = (4/2) cm = 2 cm Height (h) of cylindrical pipe = 77 cm Curved Surface Area of inner surface of pipe = 2 r1h = (2 22/7 2 77) cm2 = 968 cm2 Ex 13.2, 3 A metal pipe is 77 cm long. The inner diameter of a cross section is 4 cm, the outer diameter being 4.4 cm. (ii) Outer curved surface area, Outer radius of cylindrical pipe =r2 = ( )/2 = (4.4/2) cm = 2.2 cm Height of cylinder = h = 77 cm Curved Surface Area of outer surface of pipe = 2 r2h = (2 22/7 2.2 77) cm2 = (2 22 2.2 11) cm2 = 1064.8 cm2 Ex 13.2, 3 A metal pipe is 77 cm long. The inner diameter of a cross section is 4 cm, the outer diameter being 4.4 cm. (iii) Total surface area, r1 = 2 , r2 = 2.2 cm, h = 77 cm Total surface area = Curved Surface Area of inner cylinder + Curved Surface Area of outer cylinder + 2 Area of base Area of base = r22 r12 = 22/7 ((2.2)2 (2)2 ) = 22/7 (4.84 4) = 22/7 (0.84) = 2.74 cm2 Total surface area = Curved Surface Area of inner cylinder + Curved Surface Area of outer cylinder + 2 Area of base = 968 + 1064.8 + 2 2.74 = 2032.8 + 5.76 = 2038.08 cm2 Therefore, the total surface area of the cylindrical pipe is 2038.08 cm2

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Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.