Three pipes A, B and C can fill a cistern in 6 hours. After workingat it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. The number of hours taken by C alone to fill the cistern is:

• 14 hours.
  
  Part filled in 2 hours =2/6=1/3
  Remaining part =2/3
  (A + B)'s 7 hour's work =2/3
  (A + B)'s 1 hour's work =2/21
  C's 1 hour's work = { (A + B + C)'s 1 hour's work }-{(A + B)'s 1 hour's work }
  =1/6 - 2/21
  =1/14
  C alone can fill the tank in 14 hours.
• 11 years agoHelpfull: Yes(1) No(0)