Pipes A and B can fill a tank in 6 and 4 hours. Pipe C can empty it in 12 hours. If all pipes are opened together, then the tank will be filled in?
Pick one.
A) 3hr B) 2hr C) 1hr D) 9/7hr E) 5/3hr
Net part filled in 1 hour = 1/6 + 1/4 - 1/12 = 1/3   The tank will be full in 3 hr   3hrnswer is 3hr
<result>A</result>
Pipes A and B can fill a tank in 6 and 4 hours. Pipe C can empty it in 12 hours. If all pipes are opened together, then the tank will be filled in?