A cistern can be filled in 8 hours, but because of an outlet it is filled in…
2023
A cistern can be filled in 8 hours, but because of an outlet it is filled in 10 hours. If the cistern is filled, then how much time the outlet takes to empty the cistern ?
Answer: B. 40 hours — Answer: 40 hours Explanation: Inlet fills the cistern in 8 hours, so inlet rate = 1/8 cistern per hour. With the outlet open the cistern is filled in 10…
- A.
50 hours
- B.
40 hours
- C.
60 hours
- D.
80 hours
Attempted by 120 students.
Show answer & explanation
Correct answer: B
Answer: 40 hours
Explanation:
Inlet fills the cistern in 8 hours, so inlet rate = 1/8 cistern per hour.
With the outlet open the cistern is filled in 10 hours, so net filling rate = 1/10 cistern per hour (inlet rate minus outlet rate).
Outlet emptying rate = inlet rate − net rate = 1/8 − 1/10 = 1/40 cistern per hour.
Time for outlet alone to empty a full cistern = reciprocal of its rate = 40 hours.