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Thread: Algebra please help

  1. #1
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    Algebra please help

    Mr S drives to a meeting 30km from meeting place he realise he is going to be 15 min late,if he continues the highest aloud speed 80km/h .
    How many minutes would he be late if he would drive 70km/h ? And at what speed should he be driving to make it in time?
    Last edited by ceedee; Apr 18th 2018 at 08:45 AM.
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  2. #2
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    Re: Algebra please help

    I assume he realizes this just as he starts the trip.

    Let $T$ be the time allowed to make the 30km trip if he is to be on time.

    $30 = 80(T+0.25)$

    $T = \dfrac 1 8~hr$

    At 70 km/hr

    $t = \dfrac{30}{70} = \dfrac 3 7 ~hr$

    $\dfrac 3 7 - \dfrac 1 8 = \dfrac{24 - 7}{56} = \dfrac{17}{56}~hr$

    So he would be $\dfrac{17}{56}~hr \approx 18.2~min$ later if he drives at 70 km/hr

    I leave the last one for you. You know how long he's got to make the trip, $\dfrac 1 8~hr$, and you know the distance. You can divide I'm sure.
    Thanks from ceedee
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  3. #3
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    Re: Algebra please help

    Thank you! I tried to make hours into seconds.
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    Re: Algebra please help

    Could you please explain where you got 0.25 from?
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  5. #5
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    Re: Algebra please help

    Quote Originally Posted by ceedee View Post
    Could you please explain where you got 0.25 from?
    really?

    $\dfrac{15}{60} = 0.25$
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  6. #6
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    Re: Algebra please help

    Quote Originally Posted by romsek View Post
    really?

    $\dfrac{15}{60} = 0.25$
    DOH!!! Too stressed out here it seems like! Thanks a million!!! :-)
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