Question 1047520
RT=D basic Travel Rate Rule


<pre>
               SPEED           TIME         DISTANCE

GOING          r              {{{d/r}}}            d

RETURN         R              {{{d/R}}}             d

ROUNDTRIP                      {{{t}}}


KNOWN VARIABLES: r, R, t
UNKNOWN:  d
</pre>

Obvious equation is summation of time.
{{{d/r+d/R=t}}}
Solve for d.