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-   -   Inequalities problem solving (https://www.askmehelpdesk.com/showthread.php?t=16094)

  • Dec 14, 2005, 06:32 PM
    phoenirius
    Inequalities problem solving
    Brandon and Pat drove from Edmonton to Saskatoon a distance of 545km. Brandon drove the first part of the trip at an average speed of 100km/h, and Pat drove the remainder at an average speed of 90km/h. If the trip took Brandon and Pat 5.75h, determine the number of hours each drove.
    I'm so lost, I have to make two inequalities, maybe on and I have no idea where to start, can anybody help?
    Thank you.
  • Dec 15, 2005, 06:43 AM
    reinsuranc
    This is not about inequalities
    Let B = number miles Brandon drove, and
    let P = number of miles Pat drove.

    We can write one equation about kilometers:

    Bx100 + Px90 = 545.

    We can also write one equation about hours:

    B + P = 5.75

    From this second, we can write: B = 5.75 - P.

    We can substitute that into the first equation for B,
    and solve for P:

    Bx100 + Px90 = 545 becomes

    (5.75 - P)x100 + Px90 = 545.

    From that we get P = 3.

    Since B + P = 5.75, then B = 2.75.
  • Dec 15, 2005, 08:29 AM
    phoenirius
    Thank you
    We're doing inequalities I never thought that it could be as simple as this.
    Thanks
  • Dec 18, 2005, 06:33 PM
    s_cianci
    let t = # of hours Brandon drove
    5.75 - t = # of hours Pat drove
    Solve the equation 100t + 90(5.75 - t) = 545
    100t + 517.5 - 90t = 545
    10t + 517.5 = 545
    10t = 27.5
    t = 2.75 hrs. Brandon drove
    5.75 - t = 5.75 - 2.75 = 3 hrs. Pat drove

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