Multiple choice

Two pipes A and B can fill a cistern in 120 minutes and 150 minutes, respectively. There is also an outlet C. If all the three pipes are opened together, the cistern gets filled in 100 minutes. How much time will be taken by C to empty full tank?

  1. 3 h 20 min

  2. 2 h 40 min

  3. 3 h

  4. 3 h 40 min
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A rate = 1/120, B rate = 1/150. Combined A+B = 1/120 + 1/150 = 9/600 = 3/200. With C, A+B-C = 1/100. So 3/200 - C = 2/200. C = 1/200. Time = 200 minutes = 3 hours 20 minutes.

AI explanation

Using the least common multiple method, let the total capacity be 600 units. Pipe A fills 5 units per minute, pipe B fills 4 units per minute, and the combined rate of all three pipes is 6 units per minute. This means the outlet C empties at a rate of 3 units per minute since 5 + 4 minus the rate of C equals 6. To empty the full 600-unit tank, pipe C takes 600 divided by 3 minutes, which equals 200 minutes or 3 h 20 min.

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