math

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a patrol boat took 2.5 hours for a round trip 12km upriver and 12km back. the speed of the current was 2 km/h. what was the speed of the boat in still water?

ps: i just need to know how to make equations from the question above. it's supposed to create equation, then use the quadratic formula to solve and find the answer.

thank you!

  • math -

    speed of boat in still water ---- x km/h
    speed of current ----- 2 km/h

    speed against current = x-2
    speed with the current = x+2

    time upriver = 12/(x-2)
    time downriver = 12/(x+2)

    equation:
    12/(x-2) + 12/(x+2) = 2.5

    hint: multiply both sides by (x+2)(x-2), simplify and you have your quadratic

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