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Thread: Dad can't solve

  1. #1
    Ibdaddyp
    Guest

    Dad can't solve

    The word problem (designated as algebra) reads:

    In his fishing boat, Nathan went downstream moving at one hour less than he went upstream the same distance. If the current is moving at 4 miles per hour, how fast can he travel on still water, if it took him three hours to make the upstream trip.

    I double checked the wording of the problem.
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  2. #2
    Site Founder MathMan's Avatar
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    Ok I think this is how you solve it:

    $\displaystyle x $ = speed he can row
    $\displaystyle c $ = speed of current
    $\displaystyle T_u $ = Time to travel Upstream
    $\displaystyle T_d $ = Time to travel Downstream
    $\displaystyle D $ = Distance traveled

    $\displaystyle Distance = Speed * Time $

    $\displaystyle Speed = x \pm c $

    Since the Distance is the same in both directions we have:

    $\displaystyle T_u(x-c) = D = T_d(x+c) $

    $\displaystyle T_u = 3 $
    $\displaystyle T_d = 2 $

    $\displaystyle 3(x-4) = 2(x+4) $
    $\displaystyle 3x-12=2x+8 $
    $\displaystyle x=20$

    So his speed is 20 miles per hour
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