Q42 of 62 Page 22

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?

Given,


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


so,


inner radius = 10 - 0.25 = 9.75 cm


Volume =


From (i) and (ii)


=


= L =79 cm


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