Results 1 to 2 of 2

Math Help - quadratic equations

  1. #1
    Newbie
    Joined
    Aug 2006
    Posts
    11

    Question quadratic equations

    a train covers a distance of 300km at a constant speed .if the speed of the train is increased by 5km/hr the journey would have taken 2 hour less.find the original speed of train?

    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by anjana
    a train covers a distance of 300km at a constant speed .if the speed of the train is increased by 5km/hr the journey would have taken 2 hour less.find the original speed of train?

    If the original speed is v \mbox{ km/hr}, then the time to travel 300 \mbox{ km} is:

    t_1=\frac{300}{v}\ \mbox{hr},

    similarly at the higher speed it would take:

    t_2=\frac{300}{v+5}\ \mbox{hr}.

    But we are told t_1=t_2+2 \mbox{ hr}, so:

    <br />
\frac{300}{v}=\frac{300}{v+5}+2<br />

    which we can rearrange to:

    <br />
-2 v^2 + 10 v - 1500=0<br />

    Which has two solutions and you need the poitive one.

    RonL
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Quadratic Equations in mod 13
    Posted in the Number Theory Forum
    Replies: 4
    Last Post: July 19th 2008, 12:14 PM
  2. Replies: 1
    Last Post: June 12th 2008, 09:30 PM
  3. quadratic equations
    Posted in the Algebra Forum
    Replies: 11
    Last Post: February 22nd 2008, 08:59 PM
  4. [SOLVED] Quadratic Equations
    Posted in the Algebra Forum
    Replies: 2
    Last Post: January 15th 2008, 09:36 AM
  5. Quadratic equations again
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: November 11th 2007, 09:18 AM

Search Tags


/mathhelpforum @mathhelpforum