Pipes A can fill a tank in 5 hours and Pipe B can fill it in 6 hours . If the two pipes are opened together, then the tank will be filled in:
Select:
A) 3 4/11 hours.
B) 2 8/11 hours.
C) 2 3/11 hours.
D) 5 2/11 hours.
E) 4 3/11 hours.
Explanation:   Pipes A can fill the tank in 5 hours . Therefore,   part filled by pipe A in 1 hour =1/5 Pipe B can fill the tank in 6 hours. Therefore,   part filled by pipe B in 1 hour = 1/6   Net part filled by Pipes A,B together in 1 hour   =1/5+1/6=11/30   i.e., the tank can be filled in 30/11=2 8/11 hours.   Answer: Option 2 8/11 hours.
<result>B</result>
Pipes A can fill a tank in 5 hours and Pipe B can fill it in 6 hours . If the two pipes are opened together, then the tank will be filled in: