The diameter of a copper sphere is 18 cm.
Question:

The diameter of a copper sphere is 18 cm. The sphere is melted and is drawn into a long wire of uniform circular cross-section. If the length of the wire is 108 m, find its diameter.

Solution:

Given that diameter of a copper sphere = 18 cm

Radius of the sphere = 9 cm

Length of the wire = 108 m = 10800 cm

Volume of cylinder = Volume of sphere

$\pi r_{1}^{2} h=\frac{4}{3} \pi r_{2}^{3}$

$r_{1}^{2} \times 10800=\frac{4}{3} \times 9 \times 9 \times 9$

$r_{1}^{2}=0.009$

r1 = 0.3 cm

Therefore Diameter = 2 × 0.3 = 0.6 cm