One pipe can fill a tank three times as fast as another pipe. If together the two pipes can fill tank in 35 min, then the slower pipe alone will be able to fill the tank in? Choose the correct answer:
A) 229  B) 787  C) 144  D) 128  E) 140
Let the slower pipe alone fill the tank in x min.   Then, faster pipe will fill it in x/3 min.   1/x + 3/x = 1/35   4/x = 1/35 =&gt; x = 140 min.   Answer: 140
<result>E</result>
One pipe can fill a tank three times as fast as another pipe. If together the two pipes can fill tank in 35 min, then the slower pipe alone will be able to fill the tank in?