Q. 423.7( 12 Votes )

What length of a solid cylinder 2 cm in diameter must be taken to recast into a hollow cylinder of length 16 cm, external diameter 20 cm and thickness 2.5 mm?

Answer :


Length of solid cylinder = L

diameter o cylinder = 2 cm

radius of cylinder =

Volume of cylinder = πr2L..............(i)

Length of hollow cylinder = 16 cm

External diameter = 20 cm

External radius =

thickness = 2.5 mm = 0.25 cm


inner radius = 10 - 0.25 = 9.75 cm

Volume =

From (i) and (ii)


= L =79 cm

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