Question 1166933
<pre>
             SPEED        TIME       DISTANCE

A to B       36           d/36          d

B to A       r            d/r           d

TOTALS               d/36+d/r          2d                   
</pre>


Average speed for whole round trip, 40 mph.


{{{(2d)/(d/36+d/r)=40}}}


{{{highlight_green(2/(1/36+1/r)=40)}}}---------simplify and solve for r.