Question 997469
RT=D relates uniform rate, time, distance.


The two vehicles passed each other at time t and the sum of distances traveled was d, the distance between the two departure points.
<pre>
              speed     time      distance
vehicle1       r         t        rt
vehicle2       r+s       t        (r+s)t
total                              d
</pre>

{{{highlight_green(rt+(r+s)t=d)}}}
{{{rt+rt+st=d}}}
{{{2rt+st=d}}}
{{{2rt=d-st}}}
{{{highlight(r=(d-st)/(2t))}}}