Yahoo Answers is shutting down on May 4th, 2021 (Eastern Time) and beginning April 20th, 2021 (Eastern Time) the Yahoo Answers website will be in read-only mode. There will be no changes to other Yahoo properties or services, or your Yahoo account. You can find more information about the Yahoo Answers shutdown and how to download your data on this help page.

Need help with math question.....?

I tried everything and cannot get this answer, its my last problem. Can someone help? Possibly explain it along the way step by step?

One morning, for her Mile Club Challenge, Colleen ran 4 miles. When she got tired, she walked 7 miles. Colleen runs 4 mph faster than she walks. If she logged 1.1 hours that day in running/walking, find her walking speed and her running speed.

3 Answers

Relevance
  • 7 years ago

    Let speed of walking be x mph

    Speed of running =x+4 mph

    4/ (x+4) + 7/x = 1.1

    4x + 7(x+4) = 1.1x ( x+4)

    4x +7x +28 = 1.1x^2 + 4.4x

    1.1x^2 - 6.6x - 28 = 0

    DIVIDE BY 1.1

    x^2 - 6x - 25.45= 0

    x^2 -6x = 25.45

    ADD 9

    x^2 -6x +9 = 34.45

    ( x - 3)^2= 34.45

    x = 3 + \/34.45 = 8.87 mph

    ANSWER 8.87 mph ( walking speed ) AND 12.87 mph ( running speed )

    CHECK

    4 /12.87 = 0.31 hours

    7/8.87 = 0.79 hours

    ADD = 1.1 hours

  • ?
    Lv 7
    7 years ago

    w = walking speed

    7/w + 4/(w+4) = 1.1

    7w+28+4w = 1.1w^2+4.4w

    1.1w^2-6.6w-28

    Use the quadratic formula

    w = 8.87

    walking = 8.87 km/h

    running = 12,87 km/h

  • 7 years ago

    4mi/(x mi/h) + 7mi/(x - 4mi/hr) = 1.1hr

    4/x + 7/(x - 4) = 1.1

    common denominators:

    4(x - 4)/x(x - 4) + 7x/x(x - 4) = 1.1x(x - 4)/x(x - 4)

    4(x - 4) + 7x = 1.1x(x - 4)

    4x - 16 + 7x = 1.1x^2 - 4.4x

    1.1x^2 - 15.4x + 16 = 0

    using quadratic formula:

    x = [15.4 +/- SQR(237.16 - 4(1.1)(16))]/2(1.1)

    x = [15.4 +/- SQR(166.76)]/2.2

    x = [15.4 +/- 12.9]/2.2

    x = 14.2, 1.25

    14.2 mi/hr is the relevant root (running speed)

    Walking speed is 4mi/hr less, so 14.2 - 4 = 10.2mi/hr

    Running speed 14.2mi/hr, walking speed 10.2mi/hr.

    - .--

Still have questions? Get your answers by asking now.