Multiple choice

In a house, there is watershed management system. The reservoir at the bottom is filled in 5 hours by three pipes containing rain water. The second pipe is twice as fast as the first pipe and the third pipe is twice as fast as the second pipe. In how many hours will the first pipe alone fill the rain water reservoir?

  1. 35 hours

  2. 32 hours

  3. 29 hours

  4. 25 hours

  5. 30 hours
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A Correct answer
Explanation

Let rates be r, 2r, 4r. Total rate = 7r. In 5 hours, work = 5 * 7r = 35r. Time for first pipe (rate r) = 35r / r = 35 hours.

AI explanation

Assuming the first pipe fills at a rate of x, the combined rate of the three pipes is x plus 2x plus 4x, which equals 7x. Since the three together fill the reservoir in 5 hours, the first pipe alone takes 7 times as long, meaning 7 multiplied by 5. Therefore, the first pipe takes 35 hours to fill the reservoir alone.

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