A, B and C can do a piece of work in 30, 40 and 20 days respectively. They start the work together but C leaves 6 days before the completion of the work. In how many days is the work done?
A)10 days B)15 days C)18 days D)12 days

• A=30
  B=40
  C=20
  LCM of 30,40,20 is 120
  
  A=120/30
  A=4
  
  B=120/40
  B=3
  
  C=120/20
  C=6
  
  C leaves 6 days before the work gets completed that means for the 6 days only B and A where working
  
  6=w/7
  w=42
  that is A and B worked 42 units of work after C left
  
  the work done with C was
  
  120-42
  =78
  
  that is in the initial days they carried out 78 units of work that is A,B,C
  to calculate the days taken by them is
  
  78/13 (where 4+3+6=13 this 4,3,6 are efficiency of A,B,C)
  6 days taken by A,B,C
  
  therefore A,B took 6 days and A,B,C also took 6 days
  toghether they took=6+6=12 days
• 3 years agoHelpfull: Yes(2) No(1)