Multiple choice general knowledge

Pipe A can fill in 20 minutes and Pipe B in 30 mins and Pipe C can empty the same in 40 mins.If all of them work together, find the time taken to fill the tank

  1. 17 1/7 mins

  2. 20 mins

  3. 8 mins

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Combined rate = 1/20 + 1/30 - 1/40 = (6+4-3)/120 = 7/120 tank per minute. Time to fill = 120/7 = 17 1/7 minutes. Pipe A fills at 5% per minute, B at 3.33%, while C empties at 2.5% per minute, giving a net fill rate of about 5.83% per minute.

Keep practicing — related questions