physics

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travelling at 90km/hr except for a 30 minute rest stop. Average speed for the trip is 78km/hr.

what is the total travelling time and what is the total distance travelled??

thanks

  • physics -

    Let D = distance traveled (km)
    T = total time of trip in hours

    90 (T-0.5) = D
    D = 78 T
    Two equations, two unknowns.
    Solve by substitutuion.

    90(T - 0.5) = 78 T
    12 T = 45
    T = 3.75 hours (3.25 of which was driving)
    D = 292.5 km

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