One pipe can fill a tank three times as fast as another pipe. If together the two pipes can fill the tank in 36 minutes, then the slower pipe alone will be able to fill the tank in?  Choose the correct answer
A) 144 min	B) 250 min	C) 196 min	D) 100 min	E) 112 min
Let the slower pipe alone fill the tank in x minutes   Then, faster pipe will fill it in x/3 minutes   1/x + 3/x = 1/36   4/x = 1/36   x = 144 min   144 minnswer is 144 min
<result>A</result>
One pipe can fill a tank three times as fast as another pipe. If together the two pipes can fill the tank in 36 minutes, then the slower pipe alone will be able to fill the tank in?