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Math Help - Wrong answer key or wrong me ?

  1. #1
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    Wrong answer key or wrong me ?

    . Two pipes running together can fill up a cistern in 3(1/3) minutes. If one pipe takes 3 minutes more than the other to fill the cistern, find the time in which each pipe would fill the cistern. [Ans: 8 min]

    But I'm getting an irrational number,

    what I did

    let time of first pipe be x and time for second pipe be x-3

    so the equation is

    1/x + 1/(x-3) = 1
    x^2 -5x + 3 = 0
    from ehre it is clear taht an irrational root is obtained.....
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  2. #2
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    I’ve just worked through the problem, and I think it should be 3\frac{1}{\color{red}13} minutes, not 3\frac{1}{3} minutes.

    Quote Originally Posted by ice_syncer View Post
    so the equation is

    1/x + 1/(x-3) = 1
    No, the equation is

    \frac{1}{x}+\frac{1}{x-3}\ =\ \frac{1}{3\frac{1}{13}}

    where \frac{1}{x} is the fraction of the cistern filled in 1 minute by one of the pipes and \frac{1}{x-3} in 1 minute by the other; \frac{1}{3\frac{1}{13}} is the fraction of the cistern filled in 1 minute by both pipes together.
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  3. #3
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    Quote Originally Posted by algebraic topology View Post
    Iíve just worked through the problem, and I think it should be 3\frac{1}{\color{red}13} minutes, not 3\frac{1}{3} minutes.


    No, the equation is

    \frac{1}{x}+\frac{1}{x-3}\ =\ \frac{1}{3\frac{1}{13}}

    where \frac{1}{x} is the fraction of the cistern filled in 1 minute by one of the pipes and \frac{1}{x-3} in 1 minute by the other; \frac{1}{3\frac{1}{13}} is the fraction of the cistern filled in 1 minute by both pipes together.
    LOL LOL thanks alot! I guess I'll report it to my math teacher
    Ice Sync
    (emo)
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