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Thread: River problem

  1. #1
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    River problem

    A "cute" li'l problem:

    A river is 1000 ft. wide and 10 ft. deep. It travels at 4 mph.
    How long will it take to discharge a cubic mile of water into the ocean.
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  2. #2
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    Re: River problem

    $\dfrac{1000}{5280}\times \dfrac{10}{5280} \times 4 = \dfrac{25}{17424}~mile^3/hr=\text{discharge rate in cubic miles per hour}$

    so it takes

    $\dfrac{17424}{25}~hr \text{ to discharge a cubic mile}$

    $\text{that's 29 days}$
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  3. #3
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    Re: River problem

    Merci Monsieur Romsek; much "shorter" than mine:

    4 mph = 352 fpm

    1 feet = 1 * 10 * 1000 = 10000 cu ft
    352 fpm = 3520000 cu ft

    1 cu mile = ~ 147,200,000,000 cu ft
    147200000000 / 3520000 = 41818 min = 697 hrs

    697 / 24 = 29 days.
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