- A10.5
- B14
- C5.25
- D28
Step-by-Step Solution
Net rate = 1/7 − 1/21 = 2/21 of the tank per hour, so it fills in 21/2 = 10.5 hours.
Answer: A) 10.5
A hotel's water tank is filled by an inlet in 7 hours and emptied by an outlet in 21 hours. Starting with an empty tank, how many hours will it take to fill if both are left open?
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
Pipe P fills a tank in 16 minutes and pipe Q in 24 minutes. Both are opened together,…A is twice as efficient as B. Working together they finish a job in 12 days. How many…A can do a work in 20 days. He works alone for 5 days and then B finishes the remaining…An inlet fills a school's sump in 8 hours, but a crack would empty the full sump in 40…Two pipes A and B can fill a tank in 20 minutes and 30 minutes respectively. Both are…