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A solid metal cylinder of radius 6 cm and height 10 cm is melted down. From the molten metal a solid cone of radius 9 cm and height 12 cm is cast, and every bit of the metal left over is used to make one solid sphere. Find the radius of that sphere in cm.

Competition practiceAreas & Volumes
  • A3
  • B6
  • C4.5
  • D2

Step-by-Step Solution

Cylinder = π × π . Cone = (1/3)π × π . Metal left = 360π − 324π = 36π . Setting (4/3)ππ gives , so cm.
Answer: A) 3

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