Pipes A and B can fill a tank in 6 and 8 hours. Pipe C can empty it in 4 hours. If all pipes are opened together, then the tank will be filled in?  Answers.
A) 3/2hr B) 24hr C) 22hr D) 20hr E) 5/3hr
Net part filled in 1 hour = 1/6 + 1/8 - 1/4 = 1/24   The tank will be full in 24 hr   Answer is 24hr
<result>B</result>
Pipes A and B can fill a tank in 6 and 8 hours. Pipe C can empty it in 4 hours. If all pipes are opened together, then the tank will be filled in?