- A21
- B40
- C8.4
- D16
Step-by-Step Solution
Net fill rate = 1/12 − 1/28 = 7/84 − 3/84 = 4/84 = 1/21 per hour, so it is full after 21 hours.
Answer: A) 21
An inlet pipe can fill a cistern in 12 hours and an outlet can empty the full cistern in 28 hours. Starting empty with both open, after how many hours is the cistern full?
Competition practiceTime & Work / Pipes
Master this topic in 30 minutes a day.
Don't just memorise the answer — build a daily practice habit.
Practice 5 Similar Questions Free →All Time & Work / Pipes practice questions
More Time & Work / Pipes practice
Two carpenters, Salim and Joseph, can each make a set of wardrobes alone in 52 days and…Usha alone can bind a set of registers in 18 days and Faisal alone in 27 days. They work…18 labourers can lay a village road in 28 days. If 24 labourers are put on the job, all…P is 50% more efficient than Q. Together they complete a task in 18 days. How many days…A borewell pump fills a farm tank in 34 hours, but a faulty valve can empty the full…