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 CBT-I Official Paper (Held On: 4 Jan 2021 Shift 1)
5.4 Lakh Users
100 Questions 100 Marks 90 Mins

Detailed Solution

Download Solution PDF

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

Latest RRB NTPC Updates

Last updated on Jun 11, 2025

-> RRB NTPC 2025 Exam Postponed. Railway Recruitment Board has rescheduled the RRB NTPC Exam for June 5, 2025 (Shift 3). 

-> RRB NTPC Exam Analysis 2025 is LIVE now. All the candidates appearing for the RRB NTPC Exam 2025 can check the complete exam analysis to strategize their preparation accordingly. 

-> The UPSC Prelims Result 2025 and UPSC IFS Result 2025 has been released @upsc.gov.in

-> The RRB NTPC Admit Card 2025 has been released on its official website.

-> Candidates who will appear for the RRB NTPC Exam can check their RRB NTPC Time Table 2025 from here.

-> The RRB NTPC CBT 1 Exam is scheduled from 5th June to 24th June 2025 as per the revised tentative exam schedule. 

-> The RRB NTPC 2025 Notification has been released for a total of 11558 vacancies.

-> A total of 3445 Vacancies have been announced for Undergraduate posts like Commercial Cum Ticket Clerk, Accounts Clerk Cum Typist, Junior Clerk cum Typist & Trains Clerk.

-> A total of 8114 vacancies are announced for Graduate-level posts in the Non-Technical Popular Categories (NTPC) such as Junior Clerk cum Typist, Accounts Clerk cum Typist, Station Master, etc.

-> Prepare for the exam using RRB NTPC Previous Year Papers.

-> Check out the Rajasthan PTET Admit Card 2025 and UPSC Prelims Result Date 2025 here.

More Mensuration Questions

Get Free Access Now
Hot Links: teen patti list teen patti game online teen patti club apk teen patti master real cash teen patti - 3patti cards game downloadable content