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    Debbie traveled by boat 5 miles up stream to fish in her favorite spot. Because of the 4 mph current, it took her 20 minutes longer to get there than to return. How fast will her boat go in still water?

    © BrainMass Inc. brainmass.com October 4, 2022, 4:49 pm ad1c9bdddf
    https://brainmass.com/math/basic-algebra/boat-travel-336442

    SOLUTION This solution is FREE courtesy of BrainMass!

    Hello and thank you for posting your question to Brainmass.

    Let the boat's speed in still water denoted by x

    Then, going upstream the speed is x-4

    The time of travel is the distance of 5 miles (in hours) is Tu = 5/(x-4)

    The speed downstream is x+4

    And the time it takes to travel 5 miles is Td = 5/(x+4)

    The time to travel downstream is 1/3 of an hour (20 minutes) shorter than going upstream.

    Therefore:

    Td + 1/3 = Tu

    5/(x+4) + 1/3 = 5/(x-4)

    Multiplying both sides by (x-4):

    5(x-4)/(x+4) + (x-4)/3 = 5

    Multiplying bit sides by (x+4):

    5(x-4) + (x-4)(x+4)/3 = 5(x+4)

    Multiplying both sides by 3:

    15(x-4) + (x+4)(x-4) = 15(x+4)

    expanding:

    15x - 60 + x^2 - 16 = 15x +60

    x^2 - 16 = 120

    x^2 = 136

    x = sqrt(136) = 11.66 mph

    The speed of the boat in still water is 11.66 mph

    I hope this helps
    Thanks again,
    Yinon

    This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

    © BrainMass Inc. brainmass.com October 4, 2022, 4:49 pm ad1c9bdddf>
    https://brainmass.com/math/basic-algebra/boat-travel-336442

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