Pipes A and B can fill a tank in 4 and 6 hours. Pipe C can empty it in 8 hours. If all pipes are opened together, then the tank will be filled in? Select:	A) 60/17 hr	B) 22/7 hr	C) 52/11 hr	D) 6 hr	E) 63/19 hr
Net part filled in 1 hour = 1/4 + 1/6 - 1/8= 7/22   The tank will be full in 22/7 hr   Answer is 22/7 hr
<result>B</result>
Pipes A and B can fill a tank in 4 and 6 hours. Pipe C can empty it in 8 hours. If all pipes are opened together, then the tank will be filled in?