A solid metallic cylindrical rod of radius 1.2 cm and length 22 cm is melted and recasted as a cylindrical wire of radius 2 mm. What is the length of the wire (in cm) ?

Correct option is B

Given:

R = 1.2 cm
L = 22 cm
r = 2 mm = 0.2 cm
Concept:
When the rod is melted and recast into a wire, the volume remains constant.

Formula for the volume of a cylinder:

Volume = π x radius^2 x height
Equation for volume conservation:

Volume of rod = Volume of wire
Substituting the values and the formula, we get:

π * R^2 x L = π x r^2 x l
Simplifying and solving for l:

l = (R^2 x L) / r^2
Substituting the given values:

l = (1.2^2 x 22) / 0.2^2
Calculating the length of the wire:

l = 792 cm