A cistern is filled in 9 hours and it takes 10 hours when there is a leak in…
2023
A cistern is filled in 9 hours and it takes 10 hours when there is a leak in its bottom, if the cistern is full , in what time will the leak empty it ?
- A.
15 h
- B.
80 h
- C.
12 h
- D.
90 h
Attempted by 16 students.
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Correct answer: D
Solution: Determine the leak's emptying time by comparing rates.
Filling tap rate = 1/9 tank per hour.
Net filling rate with the leak = 1/10 tank per hour.
Leak rate (outflow) = filling rate − net rate = 1/9 − 1/10 = 1/90 tank per hour.
Time for leak alone to empty a full cistern = 1 ÷ (1/90) = 90 hours.
Answer: 90 hours