Multiple choice

A tap can empty a tank in 60 minutes. A second tap can fill it in 30 minutes. If both the pipes operate simultaneously, how much time is needed to fill the tank completely? एक नल एक टंकी को 60 मिनट में खाली कर सकता है | एक दूसरा नल इसे 30 मिनट में भर सकता है, यदि दोनों एकसाथ चालू कियें जाएँ तो टंकी को पूर्णतया भरने के लिए कितना समय लगेगा ?

  1. 40 minutes/ मिनट

  2. 45minutes /मिनट

  3. 50 minutes/मिनट

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

Empty tap rate = -1/60 tank per minute, fill tap rate = +1/30 tank per minute. Combined rate = 1/30 - 1/60 = 1/60 tank per minute. Time = 60 minutes. Option A (40 min) would require combined rate 1/40, option B (45 min) requires 1/45, option C (50 min) requires 1/50 - none match the actual rates.

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