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Homework Help: Filling a tank

  1. May 11, 2010 #1
    1. The problem statement, all variables and given/known data

    "A tank can be filled in 6 hours using 2 pipes. The larger pipe alone would fill it 5 hours sooner than the smaller pipe alone. How long would each pipe alone take?"

    2. Relevant equations

    I know it involves a quadratic not sure on the rest... I cant see how to do with a quadratic i mean.

    3. The attempt at a solution
    assume a is the big pipe and b is the small
    A=B+5 solved them to get a=11/2hours and b=1/2, i can see thats not right. i said that a was the bigger one and my answer says that its not????
  2. jcsd
  3. May 11, 2010 #2

    This website may help you


    So using the the equation form the website you get

    1/a + 1/a+5 = 1/6

    This simplifies to

    (2a+5)/a(a+5) = 1/6

    which simplifies down to the quadratic a^2 – 7a -30 = 0
  4. May 11, 2010 #3
    ok thanks
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