Three pipes of same capacity A,B,C can fill a tank in 14 hours. If there are only two pipes C and A of same capacity, the tank can be filled in?
Choose the most appropriate option:  A) 6  B) 12  C) 28  D) 42  E) 21
The part of the tank filled by three pipes in one hour   = 1/14   =&gt; The part of the tank filled by two pipes in 1 hour   = 2/3 * 1/14= 1/21.   The tank can be filled in 21 hours.   Answer:21
<result>E</result>
Three pipes of same capacity A,B,C can fill a tank in 14 hours. If there are only two pipes C and A of same capacity, the tank can be filled in?