Pipe A can fill a tank three times faster than pipe B. If both pipes A and B are running together, they can fill the tank in 12 minutes, then the time taken by pipe B alone to fill the tank is:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 48 minutes
Let pipe B alone fill the tank in t minutes. Pipe A is three times as fast, so it takes \(\frac{t}{3}\) minutes. Adding the work done per minute:
\( \displaystyle \frac{3}{t} + \frac{1}{t} = \frac{1}{12} \)
\( \displaystyle \frac{4}{t} = \frac{1}{12} \)
\( t = 48 \)
So pipe B alone takes 48 minutes (and pipe A alone 16 minutes).