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?
Here, r = Internal radius
R = External radius = 10 cm
h = Length of the cylinder
t = Thickness = 0.25 cm
Volume of the hollow cylinder = πh(R – r) = π (16) (10 – (10-0.25)) = 79 π cm
Volume of the solid cylinder = Volume of the hollow cylinder
We know that the radius of the solid cylinder is 1 cm.
∴ π(1)h = 79 π
h = 79 cm
Hence, length of the solid cylinder that gives the same volume as the hollow cylinder is 79 cm.