Multiple choice

A cistern can be filled by a pipe in 40 hours. A tap draws water at the rate of 40 litre per hour. Now the cistern is filled in 50 hours, the capacity of cistern (in liters) is?

  1. 9000

  2. 8400

  3. 8000

  4. 7200

  5. 7600
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let capacity = C liters. Pipe fill rate alone = C/40 L/hr. With tap draining 40 L/hr, net rate = C/50 L/hr. So: C/40 - 40 = C/50. Multiply by 200: 5C - 8000 = 4C, giving C = 8000 liters. The tap alone would drain the cistern in 8000/40 = 200 hours.

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