Question 1147421
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Let "d" be the unknown one-way distance, in miles.


Then the average speed biking up was  {{{d/3.5}}}  mph;  the average speed of return trip was  {{{d/2.5}}} mph.


The difference in average rates was 2 mph


    {{{d/2.5}}} - {{{d/3.5}}} = 2  mph.


It is your basic equation.


To solve it, first simplify the equation


    {{{(2d)/(2*2.5)}}} - {{{(2d)/(2*3.5)}}} = 2,   or

    {{{(2d)/5}}}   - {{{(2d)/7}}}    = 2.


Next, multiply both sides by 35. You will get


    (2d)*7 - (2d)*5 = 70

    14d    - 10d    = 70

     4d             = 70

      d             = {{{70/4}}} = 17.5  miles.     <U>ANSWER</U>
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Solved.