Six pipes are fitted to a water tank. Some of these are inlet pipes and the others outlet pipes. Each inlet pipe can fill the tank in 9 hours and each outlet pipe can empty the tank in 6 hours. On opening all the pipes, an empty tank is filled in 9 hours. How many inlet pipes are there? Answers.
A) 2 B) 4 C) 3 D) 5 E) 6
x / 9 – y / 6 = 1/9; 2x – 3y + 2   We can compute that x = 4 and y = 2.   Thus, Inlet pipe = x = 4.   Answer: 4
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Six pipes are fitted to a water tank. Some of these are inlet pipes and the others outlet pipes. Each inlet pipe can fill the tank in 9 hours and each outlet pipe can empty the tank in 6 hours. On opening all the pipes, an empty tank is filled in 9 hours. How many inlet pipes are there?