A hollow metallic cylinder whose external radius is \(4.3 \ cm\) and internal radius is \(1.1 \ cm\) and whole length is \(7 \ cm\) is melted and recast into a solid cylinder of \(21 \ cm\) long. Evaluate the diameter of solid cylinder.
 
Answer:
 
Volume of the solid cylinder is given by cu.units.
 
Volume of the hollow metallic cylinder is given by cu.units.
 
The diameter of solid cylinder \(=\)  \(cm\)