It takes Ginny's motor boat?

It takes Ginny's motor boat 4 hours to travel downstream 20 miles and 2 hours to travel 2 miles upstream from her camp. What is the average speed of the current?

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  • 7 years ago
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    4(s + c) = 20 or 4s + 4c = 20

    2(s - c) = 2 or 2s - 2c = 2 or s = 2 + c

    substitute second equation into first equation:

    4(2 + c) + 4c = 20

    8 + 4c + 4c = 20

    8c = 12

    c = 12/8 = 1.5 mi/hr

    The current speed is 1.5 miles per hour.

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