A sphere of radius 42 cm is melted and recast into a cylindrical wire of radius 21 cm. Find the length of the wire.

  1. 224 cm
  2. 320 cm
  3. 322 cm
  4. 280 cm

Answer (Detailed Solution Below)

Option 1 : 224 cm
Free
RRB NTPC Graduate Level Full Test - 01
100 Qs. 100 Marks 90 Mins

Detailed Solution

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Given:

Radius of Sphere = 42 cm

Radius of wire = 21 cm

Formula:

Volume of cylinder = πr2h

Volume of sphere = [4/3]πr3

Calculation:

Let length of the wire be x, then

According to the question

π × 21 × 21 × x = [4/3] × π × 42 × 42 × 42 [As volume will remain constant]

⇒ x = (4 × 42 × 42 × 42)/(21 × 21 × 3)

⇒ x = 224 cm 

∴ The length of the wire is 224 cm

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