Multiple choice

Pipe A can fill a tank in 3 minutes and pipe B can fill it in 4 minutes. How long would it take to fill the tank, if both the pipes work together?

  1. 12/7 minutes

  2. 7 minutes

  3. 3.5 minutes

  4. None of these
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A Correct answer
Explanation

Pipe A rate = 1/3, Pipe B rate = 1/4. Combined rate = 1/3 + 1/4 = 7/12. Time = 1 / (7/12) = 12/7 minutes.

AI explanation

Using the formula for combined work, the part of the tank filled in one minute by both pipes is the sum of their individual rates, giving 1/3 + 1/4. Finding a common denominator yields 4/12 + 3/12 = 7/12. The total time to fill the tank is the reciprocal of this combined rate, so the tank fills in 12/7 minutes.

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