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Thread: Another word problem

  1. #1
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    Another word problem

    A river flows at 2km/h, and John takes 6h to row 16km up the river and 16 km back, how fast did he row?

    I need to know how to answer a word problem like this on a test tomorrow... can someone explain to me how to solve it? also, any possible tips on solving word problems would be great, thanks
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by sugar_babee
    A river flows at 2km/h, and John takes 6h to row 16km up the river and 16 km back, how fast did he row?

    I need to know how to answer a word problem like this on a test tomorrow... can someone explain to me how to solve it? also, any possible tips on solving word problems would be great, thanks
    Let Johns speed with respect to the water be $\displaystyle v$km/h, then when
    rowing with the flow he is travelling at $\displaystyle (v+2)$km/h, and against the flow
    $\displaystyle (v-2)$km/h.

    He rows $\displaystyle 16$km with the flow and $\displaystyle 16$km against the flow.
    These take $\displaystyle 16/(v+2)$h, and $\displaystyle 16/(v-2)$h respectively
    and their total is $\displaystyle 6$h.

    So we have:

    $\displaystyle
    \frac{16}{v+2}+\frac{16}{v-2}=6\ \ \ \dots (1)
    $.

    Now we have translated the word problem into a mathematical problem, it
    remains to solve $\displaystyle (1)$, and check which of the answers make
    sense for this problem

    RonL
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  3. #3
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    Thanks a lot, thats great
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