Multiple choice

When three pipes are kept open, the tank is filled in 12 hours.If one tap can fill it in 10 hours and second in 15 hours. in how many hours can the third empty it ? जब तीन पाइप खुली रखी जाती है तो एक टैंक 12 घंटे भर जाती है। यदि एक पाइप 10 घण्टे में और दूसरी पाइप 15 घण्टे में भर सकती है तो तीसरी पाइप कितने समय में खाली कर सकती है?

  1. 10 hours/घंटे

  2. 12 hours/घंटे

  3. 15 hours/घंटे

  4. 18 hours/घंटे
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

First pipe fills at 1/10 tank per hour. Second fills at 1/15 per hour. Combined all three fill at 1/12 per hour. Third pipe empties, so: 1/10 + 1/15 - 1/t = 1/12. Solving: 3/30 + 2/30 - 1/t = 1/12. So 5/30 - 1/t = 1/12, giving 1/6 - 1/t = 1/12. Therefore 1/t = 1/6 - 1/12 = 1/12, meaning t = 12 hours. Option B is correct.

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