Pipes A and B can fill a tank in 8 and 24 hours respectively. Pipe C can empty it in 12 hours. If all the three pipes are opened together, then the tank will be filled in:
Choose the correct choice from the following:
A) 12 hr
B) 28 hr
C) 23 hr
D) 24 hr
E) 24 hr
Explanation :   Part filled by pipe 12 hr in 1 minute = 1/8   Part filled by pipe B in 1 minute = 1/24   Part emptied by pipe C in 1 minute = 1/12   Net part filled by pipe 12 hr, pipe B and pipe C in 1 minute = 1/8+1/24−1/12=2/24=1/12   i.e, the tank will be filled in 12 minutes   12 hrnswer is 12 hr
<result>A</result>
Pipes A and B can fill a tank in 8 and 24 hours respectively. Pipe C can empty it in 12 hours. If all the three pipes are opened together, then the tank will be filled in: