A copper wire 36 m long with a diameter of 2 mm is melted to make a sphere. Then the radius of the sphere is ______.
3 cm
The wire is a cylinder; on melting, its volume equals the volume of the sphere.
Radius of wire = 2 mm ÷ 2 = 1 mm = 0.1 cm
Length of wire = 36 m = 3600 cm
Volume of wire = π × (0.1)² × 3600
= 36π cm³
Volume of sphere = (4/3)πr³ = 36π
r³ = 36 × 3/4 = 27
r = 3 cm
Hence, 3 cm.
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