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A tank of 425 liters capacity has been filled with water through two pipes, the first pipe having been opened 5 hours longer than the second. If the first pipe were open as long as the second pipe, the first pipe deliver half the amount of water delivered by second pipe; if the two pipes were open simultaneously, the tank would be filled up in 17 hours. How long was the second pipe open?

  • a. 10
  • b. 12
  • c. 15
  • d. 18
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up vote 1 down vote accepted

x = first pipe rate
y = second pipe rate
a = hours of second pipe

$$y = 2x\\ 17(x+y) = 425\\ x+y = 25\\ 3x = 25\\ x = \frac{25}{3}, y = \frac{50}{3}\\ (a+5)\frac{25}{3} + a\frac{50}{3} = 425\\ (a+5) + 2a = 51\\ 3a + 5= 51\\ 3a = 46\\ a = 46/3$$

Are you allowed rounding?

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thanks a lot...yes rounding is allowed – Ritabrata Gautam Oct 21 '13 at 10:29

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