Multiple choice

Pipes P and Q can fill a tank in 12 hours and 36 hours, respectively. If both pipes are opened, then how much time (in hours) will be taken to fill the tank?

  1. 9

  2. 8

  3. 10

  4. 7
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A Correct answer
Explanation

Rate of P = 1/12, Rate of Q = 1/36. Combined rate = 1/12 + 1/36 = 3/36 + 1/36 = 4/36 = 1/9. Time = 9 hours.

AI explanation

Using the formula for combined work, if two pipes fill a tank in x and y hours, the time taken together is xy divided by (x + y). Substituting the given values gives 12 multiplied by 36, divided by the sum of 12 and 36, which equals 432 divided by 48. This simplifies to 9 hours.

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