One tap can fill a water tank four times as fast as another tap. If together the two taps can fill the water tank in 30 minutes then the slower tap alone will be able to fill the water tank in _______ . Choose the correct choice from the following answers.
A) 120 min B) 150 min C) 170 min D) 190 min E) 250 min
Let the slower pipe alone fill the water tank in t minutes.   Then, faster pipe will fill it in t/4 minutes.   Therefore, 1/t + 4/t = 1/30   =&gt;5/t = 1/30   Now solve for t.   =&gt; t=150 min   ANSWER:150 min
<result>B</result>
One tap can fill a water tank four times as fast as another tap. If together the two taps can fill the water tank in 30 minutes then the slower tap alone will be able to fill the water tank in _______ .