A solid cuboid of iron with dimensions 53 cm × 40 cm × 15 cm is melted and recast into a cylindrical pipe. The outer and inner diameters of pipe are 8 cm and 7 cm respectively. Find the length of pipe.
Outer and inner radius of the pipe: r’ = 8/2 = 4cm and r’’ = 
cm
Volume of cuboid = volume of pipe
L b h = π h[R2 – r2]
⇒ h = 2698.18cm ≈ 27m
53