A cylinder, a cone and a sphere are of the same radius -Maths 9th

A cylinder, a cone and a sphere are of the same radius -Maths 9th
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Let r be the common radius of a cylinder, cone and a sphere.  Then, height of the cylinder = Height of the cone = Height of the sphere = 2r  Let 'I' be the slant height of the cone. Then l = root under( √r2 + h2) = root under( √r2 + (2r) =  √5r Also, S1 = Curved surface area of cylinder = 2 πrh = 2 πr. 2r = 4 πr2 S2 = Curved surface area of cone = πrl = πr √5r = √5 πr2 S3 = Curved surface area of sphere = 4 πr2 Now, S1 : S2  :S3 = 4 πr2 : √5 πr2 : 4 πr2  ∴  S1 : S2 : S3 = 4 : √5 : 4
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