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The radius of a sphere is 6 cm. It is melted and drawn into a wire of radius 0.2 cm. The length of the wire is
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- 81 metre
- 80 metre
- 75 metre
- 72 metre
- 81 metre
Correct Option: D
In both cases, volume will remain same.
| Volume of sphere = | πr³ | |
| 3 |
| = | π(6)³ | |
| 3 |
= 288π cu. cm.
If the length of wire be h cm., then
⇒ πR²h = 288π
⇒ (0.2)² × h = 288
| ⇒ h = | = 7200 cm. | |
| 0.04 |
= 72 metre
