Multiple choice

A cistern usually can be filled by a tap in 15 hrs but due to a leak in the bottom it takes 3 hrs more to fill. If the tank is half filled find, in how many hours leak will empty it. एक टंकी एक नल द्वारा सामान्यता 15 घंटे में भर जाती है परन्तु तली में रिसाव के कारण इसे भरने में 3 घंटे अधिक लगते हैं. यदि टंकी आधी भरी हो तो रिसाव के कारण कितने घंटे में खाली हो जायेगी?

  1. 24

  2. 25

  3. 30

  4. 45

  5. None of these इनमे से कोई नहीं
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The tap fills at 1/15 per hour. With the leak, effective rate is 1/18 per hour (3 hours longer). Leak rate = 1/15 - 1/18 = 1/90 per hour. So leak alone empties full tank in 90 hours. Half tank will empty in 90/2 = 45 hours. Option D is correct.

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