Three pipes A, B and C can fill a tank in 6 hours. After working at 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 tank is:	Pick one:  A) 10  B) 12  C) 14  D) 16  E) 18
Explanation:   A,B,C together fill the tank in 6 hours.   =&gt; Part filled by pipes A,B,C together in 1 hr =1/6   All these pipes are open for only 2 hours and then C is closed.   Remaining part =1−1/3=2/3   This remaining part of 2/3 is filled by pipes A and B in 7 hours   Therefore, part filled by pipes A and B in 1 hr   =(2/3)/7=2/21   Part filled by pipe C in 1 hr   =(1/6-2/21)=7-4/42 =3/42 =1/14   i.e., C alone can fill the tank in 14 hours.   Answer: Option 14
<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 and A and B can fill the remaining part in 7 hours. The number of hours taken by C alone to fill the tank is: