The diameter of a copper sphere is 18 cm. It is melted and drown into a long wire of uniform cross section. If the length of the wire is 108 m, find its diameter.
Given,
Diameter of sphere = 18 cm
Length of wire = 108 m = 10800 cm
Radius of copper sphere = 
m = 36 m
Volume of sphere = 
πr3 = 
× π × 9 × 9 × 9cm3 = 972π cm3
Let the radius of wire be r cm
= πr2l = πr2 × 10800
But the volume of wire = volume of sphere
⇒ πr2 × 10800 = 972π
r2 = 
= 0.09 cm2
r = 
cm = 0.3
Hence, the diameter = 2r = 0.6 cm
18