A and B can do a piece of work in 72 days; B and C can do it in 120 days; A dn C can do it in 4 days. Who among these will take the least time if put to do it alone?

A) 80 days B) 100 days C) 120 days D) 150 days

• I think data is wrong. some typing mistake is there .
  
  If A and C can do it in 4 days, then one of A or C can do it alone in less than 8 days.then group having that person will not take more than 8 days which is not the case.
• 13 years agoHelpfull: Yes(15) No(2)
• 2(A+B+C)=1/72+1/120+1/4
  A+B+C=49/360
  C=49/360 - 1/72=44/360
  B=49/360 - 1/4= -41/360
  A=49/360 - 1/120=46/360
  Here B is -(ve) , wrong question.
• 11 years agoHelpfull: Yes(6) No(2)
• Answer is c)120 days.
• 13 years agoHelpfull: Yes(5) No(6)
• Can u please tell me how?
• 13 years agoHelpfull: Yes(4) No(2)
• c) 120 days for A will be the answer
  if
  statement is
  
  A and C can do it in '90' days.
• 13 years agoHelpfull: Yes(3) No(0)
• Good observation, Mr. S. Singh.
  
  It means one of A/C is really very fast.
  
  Then the group having that person should not take more than 8 days.
• 13 years agoHelpfull: Yes(2) No(0)
• Mr. Vignesh can definitely give some logic for 120 days as least time for fastest person..
  
  But even if two persons with min time of 120 days work together, they will take at least 60 days.
  
  How will he justify for only 4 days taken by A and C ?
• 13 years agoHelpfull: Yes(1) No(0)
• some data is missing......like "A and C do it in 4 days".it can't happened.
• 13 years agoHelpfull: Yes(1) No(0)
• (A, B & C) – (B & C) → 1 day → (1/60 – 1/120)th work
  
  A → 1/120th work
  
  A → 1 work = 120 days
• 9 years agoHelpfull: Yes(1) No(0)