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Thread: Distance formula confusion

  1. #1
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    Question Distance formula confusion

    The question below states that at noon, Deirdre and Donovan were 1100 miles apart? According to the question, Deirdre boarded the train at 12pm and Donovan 2 hours later. Is there a typo in this book or am I missing something?

    Deirdre and Donovan are in love and will be meeting in Kansas City to get married.
    Deirdre boarded a train at noon traveling due east toward Kansas City. Two hours later, Donovan boarded a train traveling due west, also heading for Kansas City, and going at a rate of speed 20 miles per hour faster than Deirdre. At noon, they were, 1,100 miles apart. At 9 pm. they, they both arrived at Kansas City. How fast are they traveling?

    Distance of Deirdre from Kansas City + Distance of Donovan from Kansas City = 1,100
    Rate x Time + Rate x Time = 1,100

    Thanks in advance.
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  2. #2
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    Re: Distance formula confusion

    Let a mph = Deirdre's speed;
    so Donovan's speed = a+20 mph

    time by Deirdre = 9 hours; so:
    distance by Deirdre = 9a;
    so distance by Donovan = 1100 - 9a

    time by Donovan = 7 hours; so:
    distance by Donovan also = 7(a + 20); so:
    1100 - 9a = 7(a + 20)

    Solve for a
    Last edited by DenisB; Jun 9th 2017 at 06:51 PM.
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