There are two pipes that can independently fill a tank in 20 minutes. Both…
2023
There are two pipes that can independently fill a tank in 20 minutes. Both these pipes are opened together and when the tank is half filled, one of them is shut. How long will it take to fill the tank from the moment when the pipes were opened ?
- A.
15 min
- B.
20 min
- C.
25 min
- D.
30 min
Show answer & explanation
Correct answer: A
Answer: 15 minutes
Explanation:
Each pipe fills 1/20 of the tank per minute, so together they fill 1/10 of the tank per minute.
With both pipes open, time to fill half the tank = (1/2) ÷ (1/10) = 5 minutes.
After one pipe is shut, the remaining half is filled by one pipe at 1/20 per minute: time = (1/2) ÷ (1/20) = 10 minutes.
Total time = 5 + 10 = 15 minutes from the moment the pipes were opened.