Question:
The diameter of a sphere is 6 cm. It is melted and drawn into a wire of diameter 2 mm. The length of the wire is
(a) 12 m
(b) 18 m
(c) 36 m
(d) 66 m
Solution:
(c) 36 m
Let h m be the length of the wire.
Volume of the sphere = volume of the wire
$\Rightarrow \frac{4}{3} \pi \times 3^{3}=\pi \times(0.1)^{2} \times h$
$\Rightarrow h=\frac{4 \times 9}{0.001}$
$=3600 \mathrm{~cm}$
$=36 \mathrm{~m}$