Question 1125034
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A van​ averages 9 miles per hour faster than a car. If the van travels 100 miles in the same time it takes the car​ to travel 70 miles, then what is the speed of each?
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A van​ averages k miles per hour faster than a car. If the van travels D miles in the same time it takes the car​ to travel d miles, then what is the speed of each?
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(Note very carefully,  {{{d<>D}}} ).


<pre>
Unknowns:  x and r

           SPEED          TIME         DISTANCE
VAN         r+k           x=D/(r+k)        D
CAR         r             x=d/r            d
</pre>
{{{D/(r+k)=d/r}}}
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{{{d(r+k)=Dr}}}
{{{dr+dk=Dr}}}
{{{Dr-dr=dk}}}

{{{r(D-d)=dk}}}

{{{highlight(r=(dk)/(D-d))}}}-----substitute your given values.