Math

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A boat travels 1 km upstream and 1 km back. The time for the round trip is 4 hours. The speed of the stream is 5 km/hr. What is the speed of the boat in still water?

  • Math -

    let speed of boat be x mph

    time upstream = 1/(x-5)
    time downstream = 1/(x+5)

    1/(x-5) + 1/(x+5) = 4
    multiply each term by (x+5)(x-5)

    x+5 + x-5 = 4(x^2 - 25)
    2x = 4x^2 - 100

    4x^2 - 2x - 100 = 0
    x = (2 ± √1604)/8
    x = 5.256 or x = a negative, which would make no sense

    the speed of the boat in still water is appr 5.26 mph

  • Math -

    a bout travels 1km upstream and 1 km downstream.it took the boat 1 hour for the round trip. the speed of the current is 2 kph. find the speed of the boat in still water.

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