Math

posted by Gary

Mark leaves the house for school walking at the rate of 4 km. per hour. Two hours later Kris follows Mark at a walking rate of 6 km. per hour. How long will Kris have to walk to overtake Mark?

  1. Reiny

    Their corresponding distances travelled is the same.

    let the time taken by Kris be x hours
    then time taken by Mark is x+2 hours

    6x = 4(x+2)

    solve for x

  2. Gary

    distance = (rate) (time)
    Mark rate is 4 kph
    Kris rate is 6 kph
    Let the time taken by Kris be  x
    And Mark be  x + 2
    Kris = Mark
    (rate) (time) = (rate) (time)
    (6) (x) = (4) (x+2)
    6x = 4(x+2)
    6x = 4x + 8
    6x – 4x = 8
    2x = 8
    x = 4 Kris needs 4 hours

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