A, B and C can do a piece of work in 24 days, 30 days and 40 days respectively. They began the work together but C left 4 days before the completion of the work. In how many days was the work completed?

• 11days
  
  Work done by A in 1 day = 1/24
  Work done by B in 1 day = 1/30
  Work done by C in 1 day = 1/40
  
  Let x be the number of days to complete the work
  Total work done = 1/24*x + 1/30*x + 1/40*(x-4)
  (5x + 4x + 3x -12)/120 = 1
  (12x-12) = 120
  12x = 132
  x = 11
  
  Number of days required to complete work = 11days
• 10 years agoHelpfull: Yes(2) No(0)
• One days work of A, B and C = (1/24 + 1/30 + 1/40) = 1/10.
  C leaves 4 days before completion of the work, which means only A and B work during the last 4 days.
  
  Work done by A and B together in the last 4 days = (4)(1/24 + 1/30) = 3/10.
  Remaining work = 7/10, which was done by A, B and C in the initial number of days.
  Number of days required for this initial work = 7 days.
  Thus, the total number of days required = 4 + 7 = 11 days.
• 10 years agoHelpfull: Yes(0) No(0)
• A's efficiency is 4.16 say 100/24=4.2 ,Similarly B's=100/30=3.3,C's =100/40=2.5
  (A+B+C) 1Days work is (4.2+3.3+2.5)=10. 10(A+B+C)*7=70 and 7.5(A+B)*4=30...
  11 Days
• 10 years agoHelpfull: Yes(0) No(0)