Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours. C is closed A and B can fill the remaining par in 7 hours. The number of hours taken by C alone to fill the tank is?	Choose the correct choice from the following answers.
A) 15 hours  B) 13 hours  C) 14 hours  D) 12 hours  E) 19 hours
Part filled in 2 hours = 2/6 = 1/3.   Remaining part = 1 - 1/3 = 2/3   (A + B)'s 1 hour work = 2/21   C's 1 hour work = [(A + B + C)'s 1 hour work - (A + B)'s 1 hour work]   = (1/6 - 2/21) = 1/14   C alone can fill the tank in 14 hours.   Answer:14 hours
<result>C</result>
Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours. C is closed A and B can fill the remaining par in 7 hours. The number of hours taken by C alone to fill the tank is?