Multiple choice

A cistern which has a leak in the bottom is filled in 15 hours. Had there been no leak, it could have been filled in 12 hours. If the cistern is full the leak can empty it in - एक टंकी जिसमें तली में छेद है, 15 घंटे में भरती है। जब टंकी में छेद न हो तो यह 12 घंटे में भरती है। यदि टंकी भरी हो तो छेद द्वारा कितने समय में खाली हो सकती है?

  1. 30

  2. 36

  3. 42

  4. 60
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Fill pipe rate: 1/12 per hour. Fill + leak together: 1/15 per hour. Therefore leak alone empties at (1/12 - 1/15) = (5/60 - 4/60) = 1/60 per hour. If the cistern is full, the leak will empty it in 60 hours.

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