Two pipes can fill a tank in 8 minutes and 5 minutes. An outlet pipe can empty the tank in 12 minutes. If all the pipes are opened when the tank is empty, then how many minutes will it take to fill the tank?
Choose the correct option
A) 30 minutes  B) 17 minutes  C) 15 minutes  D) 10 minutes  E) 14 minutes
Part of the filled by all the three pipes in one minute   = 1/8 + 1/5 - 1/12 = (15 + 24 - 10)/120 = 29/120   So, the tank becomes full in 14 minutes.   Answer: 14 minutes
<result>E</result>
Two pipes can fill a tank in 8 minutes and 5 minutes. An outlet pipe can empty the tank in 12 minutes. If all the pipes are opened when the tank is empty, then how many minutes will it take to fill the tank?