Pipe A fills a tank in 4 hours; pipe B empties it in 6 hours. If both are open, how long to fill the tank?

  1. 14 hours
  2. 2 hours
  3. 12 hours
  4. 2.4 hours
Answer

C) 12 hours

Net filling per hour = tfrac14 - tfrac16 = tfrac224, so time = 12 hours.

Quantitative Reasoning MCQ · More Speed, Time, Work & Ages MCQs · Practise