Question

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

Answer 1

solid cylinder
d=2cm
r=1cm
h=?

hollow cylinder
h=16cm
external d=2cm
,, R=1cm
internal d=2cm-(2mm+2mm)
=1.6cm
,, r=0.8 cm
volume of hollow cylinder=pi×h(R2+r2)
=3.14×16(1-0.8)
=3.14×16×0.2
=9.856 square cm

volume of solid cylinder = volume of hollow cylinder

3.14×1×h=9.856
h=9.856/3.14
h=3.136cm